The effect on the concentrations of specific serum proteins and tumour markers, of heat-treating samples at 56 degrees C for 30 min to inactivate HIV, was investigated. Statistically significant decreases, that may affect clinical decisions, were observed for alpha-1-antitrypsin, beta-2-microglobulin, IgE, fibrinogen, C1-esterase inhibitor and CA125. Statistical, but not clinically significant, changes were observed for alpha-1-acid glycoprotein, C3, haptoglobin, IgA, IgG, IgM and transferrin. A significant decrease in the alpha-1 band was observed on protein electrophoresis.