The effect of aspirin (ASP) on the binding of ascorbic acid (AA) to bovine serum albumin (BSA) has been investigated by the method of dynamic dialysis. Scatchard plots were constructed which confirmed that binding with AA occurred in the presence of BSA. When ASP was also present, greater curvature of the plot was demonstrated indicating that less binding of AA to BSA was taking place. The limiting slopes of the plots showed that ASP displaces both primary and secondary sites previously occupied by AA and that the strengths of both primary and secondary sites increased as a result of interaction with ASP. It is concluded that primary sites for binding of AA to BSA consist of two or more types of similar binding strengths, and that secondary binding also may involve binding on two or more sites. The pathophysiological implications are discussed.