An infant with monosomy-21 lived for 20 minutes. The clinical and radiologic findings suggested arthrogryposis, Infants with monosomy-21 have severe intrauterine growth retardation, failure to thrive, arthrogryposis-like findings with restriction of joint mobility, often with joint dislocations, and flexion deformities and malposition of the fingers and toes. Features which help to distinguish it from arthrogryposis include a rather specific craniofacial configuration with a broad base of the nose, an antimongoloid slant of the palpebral fissures, a down-turning mouth shaped like that of a carp, micrognathia, and large low-set ears. The condition is not associated with advanced maternal age. Radiologic findings to date have been quite variable.