We analyzed the records of 153 Guadeloupean children with sickle cell anemia (SCA), for whom clinical and laboratory data were prospectively collected (mean follow-up duration 8.4 +/- 4.6 yr). Prevalence and age-specific frequencies of acute clinical events were determined and correlations between complications, hematological parameters and potential modulating factors investigated. Painful crisis and acute chest syndrome (ACS) were the two most common complications, affecting 65.4% and 58.8% of the patients, respectively. The frequency of acute anemia was 49.7% (acute splenic sequestration 24.8%; acute aplastic anemia 15.0%). Prevalences of septicemia-meningitis and osteomyelitis were 15.7% and 16.3%, respectively. A higher incidence of infections, painful crises and acute anemia was detected in patients who developed ACS. The well-documented protective effect of HbF level on the overall disease expression was observed with higher HbF level in asymptomatic than in symptomatic patients (17.5% +/- 8% vs. 9.9% +/- 6.4%, P = 0.01) with similar ages and sex ratio. It was also confirmed on ACS and, for the first time, further extended to acute anemic events and septicemia. Besides its effect on hematological parameters, alpha-thalassemia seems to have little impact on the prevalence of complications, as do beta(S)-globin haplotypes. Comparison with other series suggests that the natural history of SCA in Guadeloupe is more similar to that in Jamaica with regard to those reported in Europe and the United States, suggesting a potential impact of environmental factors on the clinical course of the disease.