One hundred and forty-two subjects underwent left hand and wrist radiography and US examination for bone age assessment during 1 and half year study. Any radiographs indicating a disease process involving the hands were excluded. Also any radiographs of a patient with a disease definitely known to delay or accelerate skeletal maturation were also excluded before the beginning of the study.Radiographs of left hand and wrist were taken according to the instructions of Greulich-Pyle, with a tube-film distance of 91.4 cm and were then, interpreted using the Greulich-Pyle atlas by one radiologist who was unaware of the chronological age. Estimated bone age was noted on a separate plain radiography chart.Radiographic and sonographic examinations of the left wrist and hand were performed within 3 day. A linear-array real-time ultrasound equipment with a 7.5 -MHz transducer (GE LOGIQ MD 400 Milwaukee, USA) was used by another radiologist who was unaware of the plain radiography results. US scans were targeted on the ossification centers and US images clearly demonstrated the initial appearance of the ossification centers of the bones. These structures appeared as hyperechoic spots causing marked acoustic shadowing. Before US examination we prepared a hand and wrist US chart for each patient. The hand and wrist US chart briefly demonstrates all carpal bones as well as phalangeal and metacarpal epiphysis (Figure 1, 2). While the wrist was in neutral position, we investigated the presence of ossification centers of the carpal bones, radius and ulna distal epiphysis, proksimal phalanx of the thumb for each patient and noted on the hand and wrist US chart. Also to demonstrate the presence of epiphysis of metacarpals and fingers, US probe was placed on each phalanx longitudinally and the visible ossification centers in the epiphysis of the metacarpals and phalanxes were noted on the hand and wrist US chart and then each phalanx scanned in transverse plane in order to determine if the epiphysis of the phalanxes are more than half as wide as their shafts. We did not made any measurement to decide if the epiphysis of the phalanxes are more than half as wide as their shafts; this was decided just visually. There were forty-five children over 6 years old age in the present study whom were excluded from the study, not only because presence of epiphysis of metacarpals and phalanxes does not show any difference but also carpal bones demonstrates distinctly convexity, concavity or flattening after this age. So the study further investigated only children up to 6 years 5 months (n=ninty-seven). The sexual differences in rate of normal skeletal development through out the period from infancy to early adulthood were large enough to necessitate separate standards for boys and girls (4). Based on Greulich-Pyle atlas, each age is grouped according to presence of the carpal bones and the ossification centers in the epiphysis of the metacarpals and phalanxes. Each visible carpal bone and ossification centers in the epiphysis of the metacarpals and phalanxes are noted on the hand and wrist US charts. It is also noted if the width of the epiphysis of the phalanxes equals half the width of the adjacent margins of their shafts. Later on the hand and wrist US charts are interpreted by using Greulich-Pyle atlas based on the following criterion derived from Greulich-Pyle atlas. For the boys we adopted the following approach derived from Greulich-Pyle atlas, and bone age is estimated according to the following criterion; By 3 months a center of ossification in both capitate and hamate is visible.By the 1 year and three months distal epiphysis of the radius is visible whereas center of ossifications are visible in the heads of second, third and fourth metacarpals, in the proximal phalanxes of the same fingers, and in the distal phalanx of the thumb are visible by 1 year and six months. By two years a center of ossification in the epiphysis of the fifth finger and in the epiphysis of the middle and distal phalanxes of the third and fourth fingers. By two years and eight months ossification centers are visible in the proximal phalanx of the thumb, in the middle phalanx of he second finger, the distal phalanxes second and fifth fingers, and in the first metacarpal and also triquetral is visible at this stage.By three years ossification has begun in the lunate, and by three years and six months the epiphysis of the distal phalanxes of the second and fifth fingers are visible. By four years, center of ossifications are present in all phalanx epiphyses and trapezium as well, and middle phalanx epiphyses of the third and fourth fingers are now slightly more then half as wide as their shafts. By five years, the epiphysis of the first metacarpal is now more than half as wide as its metaphysis, and epiphysis of the distal phalanx of the fifth finger is now about two-thirds as wide as its shaft.By six years, ossification in the ulnar epiphysis is visible, as well as trapezoid and scaphoid .For the girls we adopted the following approach derived form Greulich-Pyle atlas, and bone age is estimated according to following criterion; By three months center of ossification is visible in both capitate and hamate and by one year, ossification center is present in the distal epiphysis of the radius. The epiphysis of the second and third metacarpals and the epiphyses of the proximal phalanxes of the second, third, and fourth fingers are visible. By one year and three months ossification is visible both in the epiphysis of the fourth metacarpal, and in the epiphysis of the distal phalanx of the thumb. By one year and six months ossification in the epiphysis of the fifth metacarpal and in the proximal epiphysis of the fifth finger are visible.By two years, ossification has began in the triquetral, and the epiphysis of the first metacarpal, and in the proximal phalanx of the thumb. And the epiphyses of the proximal phalanxes of the second, third, fourth, and fifth fingers are now more than half as wide the shafts. Ossification has begun in the epiphysis of the distal phalanxes of the third, fourth and fifth fingers. By two years and six months the epiphysis of the distal phalanx of the second finger and middle phalanx of the fifth finger are visible.By three years, ossification has began in the lunate. The epiphysis of the middle phalanxes of the second third, and fourth fingers are now slightly more than half as wide as their shafts. By three years and six months, a tiny center of ossification is visible in the trapezium.By four years, ossification is visible in the scaphoid and trapezoid.By five years, the distal phalanx epiphysis of the third, fourth, and fifth fingers are now as wide as their shafts.By six years, an ossification center is now present in the distal epiphysis of the ulna.Briefly, to plot the data, and draw the line of equality on which all points would lie if the two methods (US and plain radiography) gave exactly the same values, both the estimated ages derived from the plain radiography chart and hand and wrist US charts for the one hundred and fifteen patients were compared statistically regression analysis.