During a systematic survey for genetic causes of mental retardation in schools for adolescents with learning problems we had the occasion to examine a 16-year-old moderately mentally retarded boy with facial dysmorphism, short stature, relative microcephaly, complete cutaneous syndactyly of fingers III/IV and of toes II/III. Partial clinical manifestations (low to subnormal intelligence and syndactyly) were present in his mother and sister. We discuss the nosology and differential diagnosis of the craniodigital syndromes.