The outcomes of drug treatment for male infertility remain conjectural, with controversial study results. Our pilot study employed a randomized, placebo-controlled, crossover methodology with intention-to-treat analysis. Thirty-three men with idiopathic oligospermia were randomized to start either daily oral lisinopril 2.5 mg (n = 17) or daily oral placebo (n = 16). Lisinopril was found to cause a normalization of seminal parameters in 53.6% of the participants. Although the mean ejaculate volume was unchanged (P ≥ 0.093), the total sperm cell count and the percentage of motile sperm cells increased (P ≤ 0.03 and P