The Fc-receptor function of the mononuclear phagocyte system (MPS) was examined in 41 children and adult patients, by measuring the clearance of IgG-sensitized, 51Cr-labeled erythrocytes. The Fc-receptor-mediated clearance observed in patients (mean ± SE) was not significantly different as compared to the control group of similar age distribution. However, the immune clearance time was significantly age-correlated in both groups (acute poststreptococcal glomerulonephritis, APSGN, r = 0.39, p < 0.05; control r = 0.63, p < 0.01l). The magnitude of the Fc-specific immune clearance and the serum creatinine were also significantly correlated (r = 0.59; p < 0.01). Circulating immune complexes (as measured by the C1q and conglutinin ELISA) did not correlate with immune clearance, which remained stable in longitudinal studies. Age-related changes in MPS Fc-receptor function could explain, at least in part, prognostic differences between children and adult patients with APSGN.