We constructed the standard growth (length/height and weight) curves for Japanese individuals with Prader-Willi syndrome (PWS). Crude height and weight data were collected from 153 males and 99 females with the syndrome, and the collected data were arranged by a mathematical method to construct the curves. Height growth patterns were quite different between PWS and normal children. Mean height of individuals with the syndrome by puberty is −2 SD for normal children, and it drops off far below −2 SD value after puberty. Final mean height is 141.2 ± 4.8 cm for females (n = 13) and 147.7 ± 7.7 cm for males (n = 17), showing 15.8 and 21.9 cm below the average height for normal Japanese girls and boys, respectively. Thus, the degree of shortness is more pronounced in male than in female patients. There was no difference in height between those with chromosome 15q deletion and those without. Mean weight at birth of girls (n = 88) and boys (n = 131) were 2.70 ± 0.45 Kg and 2.62 ± 0.47 Kg, respectively. These values were smaller than those for normal neonates (P < 0.05, t-test). The weight of PWS children was under the mean value for normal infants by age 2 years, but gradually increase above the mean values for normal children around ages 2–4 years. Overweight in both males and females becomes obvious during prepuberty. Growth patterns are not different between Japanese and Caucasian children with the syndrome. Short stature is more prominent in boys of both ethnic groups, whereas the degree of overweight appears much more severe in Caucasians. Am. J. Med. Genet. 95:130–134, 2000. © 2000 Wiley-Liss, Inc.