To investigate the association between four functional polymorphisms in interleukin-1 (IL-1) [IL-1 alpha -889 C/T, IL-1 beta +3953 C/T, IL-1RA (86 bp)n] and tumor necrosis factor alpha (TNFalpha) (-308A/G) genes and suicide attempts. Distribution of the aforesaid polymorphisms was analyzed in 193 suicide attempters compared with 420 unrelated healthy controls from Asturias (Northern Spain). Genotypes were determined using standard methods. No significant differences were found in genotype or in allelic distribution of IL-1 alpha, IL-1 beta, IL-1RA, or TNFalpha gene polymorphisms. No relationship was found between genotypes and the impulsivity of the suicide attempt. Estimated IL-1 haplotype frequencies were similar in both groups (likelihood ratio test=13.26, df=14, P=0.506). Our data do not suggest that genetically determined changes in the IL-1 or TNFalpha genes confer increased susceptibility to suicidal behavior.