The periodontal status of patients with reduced immunocapacity was assessed. Gingival inflammation, periodontal destruction, and plaque accumulation were compared in three groups--renal transplant patients, dialysis patients, and normal individuals. The levels of all parameters were similar in the three groups indicating that immunosuppression does not affect the clinical appearance of periodontal disease when measurements are made in a single examination. In the transplant group, however, there is a lack of correlation between P.I. and G.I. and between P.I. and P.D.I., indicating a dissociation between plaque accumulation and the tissue response. Long-term longitudinal studies of periodontal disease in such patients are needed in order to obtain more meaningful information on the role of the immune system in affecting the rate of periodontal destruction. This study suggests that nonimmune mechanisms such as the direct effect of bacterial products on supporting tissues can account for at least some of the clinical manifestations of periodontal disease.