METHODS Prospective longitudinal study. OBJECTIVE To assess the impact of spinal cord injury (SCI) on the spermatogenesis of patients studied in the early subacute stage and ensuing months. METHODS National hospital for SCI patients. METHODS A prospective follow-up study was conducted on 28 male patients with complete SCI who were evaluated in the early subacute phase (~1 month), and 3 and 6 months after the injury. At each time point, fine needle aspiration biopsy samples were taken from the testes for cytological assessment, and serum levels of relevant hormones were measured. At the end of the study period, ejaculation was attempted for standard semen analyses. RESULTS Cytological patterns indicative of defective spermatogenesis were found in 61%, 52% and 20% of the patients at 1, 3 and 6 months after SCI, respectively, suggesting an improvement over time. Serum hormone analyses showed a steady elevation of estradiol levels above the reference range, and increasing levels of testosterone, inhibin B and prolactin throughout the study period. Prolactin levels were above the reference range at all time points. Only 2 out of the 10 patients who were able to ejaculate at 6 months post injury showed normal sperm parameters. CONCLUSIONS A majority of the patients showed impaired spermatogenesis soon after the injury, which in most cases recovered over time. That was accompanied by parallel increases in serum levels of inhibin B, testosterone and prolactin, possibly driving or reflecting the spermatogenesis recovery. Further studies are needed to elucidate the biological mechanisms underlying these changes.