Congenital dyserythropoietic anemia and chronic recurrent multifocal osteomyelitis, uncommon childhood diseases of unknown cause, occurred in three children (two brothers and a female cousin). Their parents are consanguineous, and the clinical course of their illness was similar. The two brothers also had Sweet syndrome. The association of Sweet syndrome with chronic recurrent multifocal osteomyelitis and congenital dyserythropoietic anemia in this family suggests that these rare conditions may be interrelated.