Thirty-nine school-age children with Down's syndrome (trisomy 21) were examined for orthopedic problems and evidence of joint laxity. Of these, 10.3% had required orthopedic surgery for feet and hip problems, and 13% had disorders not yet requiring surgery. Only two children could be regarded as showing unequivocally abnormal generalized joint laxity. Twenty-three of the children had one or more lax joints, and one had a dislocated hip without laxity of other joints. Six children had hypermobility of the patella, but this did not correlate with joint laxity. Fifteen children had no evidence of joint laxity. Laxity does not appear to be a major etiological factor in joint problems occurring in Down's syndrome.