Lymphocyte subpopulations in thirty patients with IgA glomerulonephritis and in twenty-four healthy persons were identified using specific monoclonal antibodies. Decreased OKT11+ cells (37.83 +/- 13.34, p less than 0.01) without any changes of OKT4+ cells, but increased OKT8+ cells (25.89 +/- 6.70, p less than 0.01) in patients with IgA glomerulonephritis, as compared to a control group, were found. The OKT4+:OKT8+ ratio was decreased in the patients (2.18 vs. 2.47 for the control group). The monocytes were increased (19.26 +/- 6.63 vs. 2.47 +/- 3.28). No statistically significant correlations between abnormal T cells or monocytes and blood pressure, serum creatinine, erythrocyte sedimentation rate and serum levels of IgA were found. It is concluded that no clear-cut correlation could be demonstrated between in vitro and clinical findings.