To determine the incidence, prevalence, and outcome of systemic lupus erythematosus (SLE) in a weli delineated black population in the Caribbean basin data were collected on the disease course of ali patients with definite SLE seen during a 10 year period (1980-9) using three different sources of information (hospital records, private practice records, and death certificates). Ninety four patients were identified giving an average annual incidence rate of 4-6/100 000 (95% confidence interval (CI) 0-4 to 8-8), which showed little variation during the study period. Twenty five patients (27%) died during the study period, giving a point prevalence of 47/100 000 (CI 34-1 to 51-1) in 1990. In women aged 15-44 years the annual incidence (12/100 000; CI 5-3 to 18.9) was highest, whereas in women aged 44-65 years the 1990 point prevalence rate (one in 526; CI 469 to 625) was highest. Annual mortality was 1-7/100 000 (CI -0-8 to 4-2) with a female to male ratio of 5-3. Renal disease was the most common complication, occurring in 73 (78%) patients. Thus the transatlantic movement from an area with a (presumably) low prevalence of SLE (Central Africa) has been accompanied by an increase in the prevalence of SLE in the black population of Curaqao, indicating that environmental factors may prevail over genetic factors in the expression of this disease.