The purpose of this research was to assess some histological parameters and activity between the left and right testis of ten adult local bulls that were collected from the Duhok slaughterhouse /Iraq. The left and right testis specimens were routinely processed and stained with hematoxylin and eosin. The tunica albuginea is a thick sheet of dense, fibrous connective tissue that covers testicular tissue. The mean thickness of the tunics of an adult local bull differed significantly (p≤0.05) between the left and right testis. Thin septa that extended from the tunica albuginea to the mediastinum testis separated the parenchyma into lobules. Tortuous seminiferous tubules were found in each lobule. The mean diameter of the rounded seminiferous tubule of the left testicle was substantially (P<0.05) larger than that the right testicle. Tubular differential index (TDI) and spermatogenesis index (SPI) were found substantially (P<0.05) higher in the left testicle than the right. Sertoli cells are roughly pyramidal in shape, with an oval nucleus. The spermatogonia were circular or cuboidal in shape and possessed a round, dark nuclei. The large spherical nuclei and granular chromatin aggregates were found in primary spermatocytes. The spherical spermatids were small and elongated spermatids were developed. Some seminiferous tubules contain both spermatids and spermatozoa. Either narrow strands of interstitial tissue among two seminiferous tubules or massive triangular and quadrangular interstitial spaces separate up to three tubules. It contains only blood capillaries, a few Leydig cells, and some fibroblast cells, or extensive vessels (blood and lymph), as well as many Leydig cells. Within inter tubular spaces, Leydig cells were found as singular or in clusters. It was concluded that the thickness of the tunica albuginea, the diameter of the seminiferous tubules, the tubular differential index, and the spermatogenesis index were higher in the left testis of local adult bulls than the right testis.