Baseline C-reactive protein (CRP) concentrations are indicative of persons prone to cardiovascular diseases and are about 40-50% heritable. We have previously shown that interleukin (IL)-1B +3954 allele T is associated with lower CRP concentration. In this study, we aimed to examine the effect of this polymorphism together with the CRP +1059 gene polymorphism on baseline CRP concentrations, and genotyped 336 healthy blood donors for CRP +1059 (G-->C) and IL-1B +3954 (C-->T) polymorphisms. In men, the carriers of the CRP +1059 C-allele had significantly lower CRP values than GG homozygotes (0.66 versus 0.43 mg l(-1), up to -35%, P = 0.009). No significant difference was found in women. When the data were stratified for both of these polymorphisms in men, CRP +1059 GG homozygotes had low CRP concentrations only if they were allele-T carriers of IL-1B +3954 simultaneously (0.93 versus 0.50 mg l(-1), P = 0.013). Genotype CRP +1059 GG/IL-1B +3954 CC was associated with an almost 3-fold risk of a higher baseline CRP value [odds ratio (OR) 2.84 (CI 1.03-6.07)]. Thus, both IL-1B +3954 (C-->T) and CRP +1059 (G-->C) polymorphisms influence baseline CRP values and act independently of each other in male subjects. These polymorphisms might be predictive markers of persons prone to cardiovascular diseases.