Prostate specific antigen (PSA) is frequently used for prostate cancer (PCa) screening, but serum levels are also increased by prostate inflammation. Elevations in serum levels of alpha1-antitrypsin (ATT), a marker of inflammation, in cancer patients are well documented. However, an association between PSA and ATT has never been investigated. The authors, therefore, measured serum acute phase proteins (APPs) ATT, alpha1-acid glycoprotein, C-reactive protein, and alpha1-antichymotrypsin in 174 men without and 34 with newly diagnosed untreated PCa (38-80 years old). As expected, men with PCa had higher mean PSA levels than those without PCa (P < 0.00001). Men with PCa and those without PCa but with PSA >2 ng/mL (n = 68) had significantly higher ATT concentrations than those without these conditions (n = 106) (mean +/- SEM g/L): 1.94+/-0.083, 1.92+/-0.066, 1.25+/-0.043, respectively; p <0.005). Interestingly, African-American men without PCa (n=111) had higher ATT levels than Caucasian men (n=63) (1.565+/-0.045 g/l versus 1.395+/-0.056 g/l; p <0.005); and differences persisted in men with PSA >2 ng/ml (2.094+/-0.07 g/l versus 1.593 for all0.095 g/l; p<0.0002). There were no differences among groups in the levels of other APP. ATT showed the strongest correlation with PSA (r = 0.346 to 0.395; p <0.001) than any other APP (r < or =0.245). Our data suggest that men with PCa have higher ATT levels than those without PCa; and African-American men without PCa have higher ATT levels than Caucasian men. The possible implications of elevated ATT levels in African-American men on the risk of PCa are discussed.