The course and prognostic value of disease activity measured by the validated Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) was investigated in 68 newly diagnosed black Caribbean cases. A high percentage of patients had clinical renal involvement (78%). Disease activity at onset was mild to moderate (SLEDAI < or = 10) in 36% of patients; about half never reached a higher SLEDAI score, whereas the other half advanced to higher disease activity (SLEDAI > 10). SLEDAI scores decreased significantly over time from diagnosis. Within 3 months after disease onset, 54% of patients reached their maximum SLEDAI scores. There were no differences in clinical features or survival between these patients and those with later (mean, 35 months) maximum disease activity, although the latter had more frequent disease flares. Overall survival was poor (91% and 56% at 1 and 5 years, respectively). High persistent disease activity (weighted average of SLEDAI scores > 10) was independently associated with decreased survival, whereas a high initial SLEDAI, a high maximum SLEDAI, and an increase number of flares were not. The main cause of death was infection, which often was associated with active disease (mean SLEDAI at death, 16 +/- 8.9). SLEDAI was a practical and reliable way of evaluating disease activity but was of limited prognostic value.