Although group A meningococcal disease is a major cause of child morbidity and mortality in sub-Saharan Africa, little is known about vitamin A status and T-cell subpopulations in affected children. A prospective study of vitamin A levels and T-cell subpopulations was conducted in 41 children hospitalized for meningococcal meningitis in Butare, Rwanda, during an epidemic from September through November, 1992. The mean age of cases was 3.6 +/- 2.7 years (range 0.5-16 years). The case-fatality rate was 20 per cent; 73 per cent of the children had serum vitamin A levels consistent with subclinical deficiency (< 0.7 mumol/l), and 27 per cent had levels consistent with severe deficiency (< 0.35 mumol/l). Mean CD4 per cent was higher and CD8 per cent was lower among children with meningitis compared with known reference populations. These results suggest that meningococcal disease is characterized by T-cell subpopulation alterations and vitamin A deficiency.