The clinical features of Stickler's syndrome are described in two families with a total of 22 affected members and compared with those of the three previously reported families. Progressive joint degeneration (85%), myopia (83%) and retinal detachment (61%) are the most frequent manifestations. Cleft palate (28%), micrognathia (17%) and sensorineural hearing loss (9%) are also liable to occur in affected individuals. Inheritance is autosomal dominant with virtually complete penetrance. Genetic counselling is extremely important and relatively straightforward since most of the findings are manifest in the first two decades of life and represent severe incapacities to the affected families. All six of the affected individuals tested had increased urinary hydroxyproline excretion, a feature that may lead to earlier postnatal and possibly prenatal diagnosis.