Reduction of O2 delivery to tissues damage them, including the seminiferous epithelium. Recently, population working in high altitude has increased, so that the study of hypobaric hypoxia on spermatogenesis becomes of interest. In this study we used two groups of male, sexually mature mice Control (C) (540 meters above sea level (masl)) and chronic simulated hypobaric hypoxia (CSHH) (4,600 masl) exposed during 8, 16, 24 or 33 days. Hematocrit; reticulocytosis; testicular, epididymal and seminal vesicle weight; seminiferous epithelium height, tubular diameter, sperm count and morphology and testicular parenchyme and spermatozoa membranes lipoperoxidation were measured. Weight of testis, epididymis and seminal vesicle were reduced but they recuperate at 33 days. Tubular diameter and epithelial height are reduced, subsequently they tend to increase without returning to normal values. The count and sperm morphology fluctuate along the exposure time. Lipoperoxidation levels of spermatozoa and testicular parenchyme are reduced. Therefore, we can conclude that exposure to CSHH induce damage in the seminiferous epithelium, decrease of lipoperoxidation in spermatozoa and testicular tissue, and damages the testicular and sperm morphology