This pilot study tested the gender-specificity of the association between suicide attempts and a polymorphism in the promoter area of the serotonin transporter with two allelic variants, a long (1) variant and a short (s) variant. In a Spanish general hospital, 180 suicide attempters (121 women and 59 men) and 212 control blood donors (93 women and 119 men) were recruited. Subjects were classified as S individuals (s/s or s/l) with low expression of the serotonin transporter, and L individuals (l/l) with high expression. S individuals were significantly overrepresented (or L, underrepresented) in female attempters when compared with female controls and male attempters. Lethality appeared to have a significant influence on the effects of the genotype in suicide since S females were overrepresented among non-lethal female attempters. Further studies are needed to replicate that the serotonin genotype polymorphism may influence suicide attempts only in females.