Abstract Objective: To determine whether antisperm autoantibody production after prepubertal vas injury is influenced by immediate repair of the vas compared to delay of the reanastomosis until sexual maturity. Design: Animal study comparing early repair, late repair, and sham-operated groups. Setting: Research laboratory in a medical school. Patient(s): Lewis rats. Intervention(s): After division of the vas deferens in juvenile rats, animals in an early repair group had the vasa repaired immediately by using an absorbable intraluminal stent. Animals in a late repair group had vasa obstructed by ligation until after puberty, when they underwent microsurgical vasovasostomy (age 60 days). Main Outcome Measure(s): Antisperm antibodies were assayed by ELISA. The weights of reproductive organs were determined, and samples of testis were studied by light microscopy. Result(s): The antisperm antibody response was less when the vas was repaired immediately than if the repair was delayed until after puberty. There was a low incidence of testicular alteration in the repair groups and none in sham-operated animals. Conclusion(s): If the vas deferens is injured or obstructed prepubertally, there may be a benefit to considering immediate repair to reduce the likelihood of developing antisperm autoantibodies, which have been associated with reduced fertility.