Age, sex and chromosome effects on weight, height, sitting height, three head dimensions, and five hand and three foot measurements were analyzed from 57 patients (35 males and 22 females) with the Prader-Willi syndrome (PWS). No significant differences were observed in anthropometric data between PWS patients with the 15q chromosome deletion and those with normal chromosomes. Preschool children were found to have dolichocephaly, while hand and foot measurements, stature and sitting height were within normal range, although foot size was smaller than hand size in females when compared with PWS males. However, anthropometric measurements, excluding weight, head length and ankle breadth, were less than -2 SD in adult patients. Abnormal growth patterns apparently exist with significant negative correlations with age, particularly in PWS males, for height, sitting height, head circumference, and hand and foot measurements, but a significant positive correlation for weight was found in patients below 10 years of age.