A father and two daughters have a distinctive form of arthrogryposis multiplex congenita in which there is neither weakness nor atrophy about the affected joints despite the existence of myopathy. Contractures of the hips arid shoulders are present in all three individuals, but only the father has severe involvement of the hands and feet. Serum creatine phosphokinase values are 1.5 and three times normal in the daughters and five times normal in the father. Although it is likely that the myopathy and arthrogryposis are due to the effects of a dominantly inherited gene that appears as a new mutation in the father, the mechanism of production of the arthrogryposis in the absence of weakness is unknown.