Serum total free radical trapping abilities (TRAP experimental) were measured in 15 patients with acute myocardial infarction (AMI) and compared to sex- and age-matched controls. TRAP experimental values were significantly lower (p less than 0.01) in the AMI group. Theoretical trapping abilities were also calculated and compared with experimentally derived values. In the AMI group there was no significant difference between the experimental and calculated TRAP, but in the control group experimental values were significantly higher (p less than 0.01) than calculated values. In the control group regression analysis revealed that alpha-tocopherol and ascorbate taken together most closely explained the radical trapping ability of sera, with a regression equation: TRAP experimental = 562.9 + 2.082 (alpha-tocopherol + ascorbate). In the AMI group no relationship between the serum antioxidants and TRAP experimental was observed.