Objective: To evaluate the immunocontraceptive properties of recombinant DE, a sperm epididymal protein involved in fertilization, via an experimental study in rats as a critical step toward the development of a human immunocontraceptive. Design: In vivo study in rats. Setting: Animal care facility of an academic research center. Animal(s): Seventy-four 90-day-old Wistar male and female rats distributed into three groups. Intervention(s): Animals received five injections (intramuscular and subcutaneous) of recombinant DE (recDE), native DE (nDE), or MBP (maltose-binding protein). At various times, animals were anesthetized and bled. Main Outcome Measure(s): Anti-DE levels and tissue specificity of sera were evaluated by enzyme-linked immunosorbent assay (ELISA) and Western blot, respectively. Fertility was analyzed by natural mating. The testes and epididymides were analyzed by histology. Result(s): Recombinant DE raised an immune response with the same kinetics and higher anti-DE levels than that elicited by nDE. Sera against recDE recognized epitopes of DE that were different from those recognized by anti-nDE sera but specifically reacted with DE in epididymis and sperm without cross-reacting with other tissues tested. Male and female recDE-injected animals presented a statistically significant reduction in their fertility with no evidence of pathologic effects. Conclusion(s): Recombinant DE is able to both elicit a specific immune response and inhibit male and female fertility, supporting the use of this sperm epididymal protein for the development of an immunocontraceptive approach.