Aflatoxins (A-flavus-toxins) are the most studied group of mycotoxins. At smaller concentrations the Aflatoxins can affect male reproduction, namely spermatogenesis. The present study was designed to investigate the effect of Aflatoxin-B1 on male reproductive system by two ways: clinically on human beings and experimentally on rabbits. Human study was conducted on 100 males attending outpatients of Andrology Clinic of Sohag University Hospitals; 50 males had normal seminogram and 50 males had abnormal seminogram. Animal study was conducted on 45 adult NZW rabbit bucks. They were divided into three groups. Each group was divided to three subgroups; (negative control, positive control and treated rabbits). Treated subgroups received Aflatoxin B1 by i.p injection at 20 ∝ g/ kg/BW per day (subtoxic dose) for different durations (30 days, 48 days and 63 days). Human study showed significant increase in seminal plasma Aflatoxin-B1 level in the infertile group. The increased AFB1 level affected significantly semen parameters. Experimental results showed significant negative correlation between the seminal AFB1 level and sperm concentration, sperm viability and total sperm motility but showed significant positive correlation with abnormal sperm forms. Histopathological examination showed degeneration of seminifrous tubules. The tubules showed absence of mature sperms with appearance of uninucleated and multinucleated giant cells. Epididymal epithelium showed vaculation and degeneration. From the obtained results, it can be concluded that Aflatoxin B1 affect male reproductive system functionally and pathologically.