Intact human erythrocytes were pretreated with glutaraldehyde, neuraminidase or a combination of both treatments, incubated with monosodium urate monohydrate (MSUM) crystals and the percent hemolysis values determined by measuring hemoglobin release from the cells. The binding of MSUM crystals to pretreated erythrocyte membranes was also quantitated. Neuraminidase treated cells gave higher percent hemolysis values than untreated cells due primarily to the increased binding of MSUM to neuraminidase treated erythrocyte membranes. Pretreatment of red cells with glutaraldehyde up to a maximum concentration of 0.015% inhibited MSUM induced hemolysis but the binding of MSUM to glutaraldehyde treated and untreated cell membranes was the same. We propose a "pore" model for MSUM induced hemolysis.