Eleven cases of sickle cell disease within the Sydney area are described. Eight of these are of homozygous sickle cell anaemia, and three are of the sickle cell-thalassaemia disease. The racial origin is Lebanese Moslem in five cases, Greek from the mainland or Cyprus in four, and Portuguese, French, and Spanish in two sisters: consanguinity occurred in the latter family, and in three of the five Lebanese Moslem families. The age of patients at diagnosis ranged from five months to 22 years, and the clinical severity from very mild to very severe, with a wide spectrum of clinical manifestations. It is concluded that sickle cell disease is already a significant health problem within the Sydney area, and likely to increase in incidence with increasing migration from endemic zones.