This study investigated the effect of sildenafil citrate on micro-recanalization and neovascularization, which were previously demonstrated in a rat model using biodegradable grafts (BGs) for vas deferens reconstruction. A total of 24 male rats underwent bilateral vasectomy with removal of a 0.5-cm vasal segment and were randomly assigned to four groups. Groups 1 and 2 underwent immediate vasovasostomy. Groups 3 and 4 underwent interposition of a 0.5-cm BG in the vasal gap. Groups 1 and 3 were given 5 mg kg -1 day -1 oral sildenafil. Other groups were given placebo. Rats were housed with females 12 weeks postoperatively. Reconstructed vasal segments were harvested 16 weeks postoperatively and analyzed histologically. Fluid from the distal vasal stump was analyzed for motile sperm. Urine samples obtained 16 weeks postoperatively were analyzed for cGMP levels. cGMP levels in rats treated with sildenafil were significantly higher than in control rats. No pregnancies were sired by grafted groups. In all, 5/6 rats in group 1 and 3/6 rats in group 2 sired litters. No motile sperm were noted in the vasal fluid of the grafted groups. Motile sperm were noted in all rats in group 1 and in 5/6 rats in group 2. In addition, 29 and 4 microcanals were detected in the sildenafil and placebo groups, respectively (P = 0.023). No microcanal exceeded 3 mm in length. An average of 12 and 28 blood vessels per graft were noted in the placebo and sildenafil groups, respectively (P 0.0001). In conclusion, sildenafil enhances micro-recanalization and neovascularization in BG used for vas deferens reconstruction, but does not increase the microcanal length after 16 weeks.