To define the effects of influenza vaccination on the glomerular filtration rate and on proteinuria in patients with glomerulonephropathies, creatinine clearances and urinary protein excretions were measured in 21 patients with glomerular diseases, before vaccination and weekly for 4 to 6 weeks afterwards. Serum and nasal secretion antibody titers were measured before vaccination and 4 weeks later. Creatinine clearances remained relatively unchanged in all patients. Minimal, transient increase in proteinuria occurred in three patients with nephrotic syndrome and in two whose nephrotic syndrome was in remission. Antibody titers rose fourfold or more in patients with normal renal function after vaccination but not in patients with renal failure (P < 0.01). Since influenza vaccination had no adverse effects on patients with glomerulonephropathies, there is no reason for withholding vaccination from such patients. Patients with glomerulonephropathies should receive influenza vaccination, since chronically ill patients with influenza infection have a high mortality.