Concerns about the worldwide decline in semen quality over the past 50 years are increasing. Western countries have shown a decline in semen quality. However, in non-Western countries studies are sparse. We investigated trends in semen parameters between 1996 and 2007 in the Sfax area of southern Tunisia in a sample of 2940 men in infertile relationships. Age at semen collection, duration of sexual abstinence, volume of seminal fluid, the sperm count, percentages of motile and morphologically normal spermatozoa, and semen leukocyte concentration were determined. Linear regression was used to examine trends over time in sperm count, sperm motility, normal morphology, and semen leukocyte concentration. Mean age and semen volume did not change between 1996 and 2007. Data adjusted for age and abstinence showed a decreasing trend in sperm count and percentage of normal morphology over the last 12 years (R(2) = 0.71, P = .0004, and R(2) = 0.87, P < .0001, respectively). There was no significant change in sperm motility. However, semen leukocyte concentration increased significantly over time (R(2) = 0.38, P = .03). These results coincide with the high prevalence of genital infectious diseases in the Sfax area, suggesting that infection may be a potential contributing factor in semen quality decline.