Abstract: This study was designed to evaluate the ultrastructure of contra lateral testis tissue and measurement of Serum inhibin B following unilateral blunt testis trauma. Twenty pre-pubertal male wistar albino rats aged 3 weeks were divided into 4 equal groups that each containing five rats. Group I was the control group. Group II was used as a Sham group. Group III had right orchiectomy initially. Group IV was the trauma group in which the right testis was placed on a firm sterile surface and the metal rod weighting 100 g was drooped on to the testis from a height of 5.5 cm. Seven weeks after initial operation 3 mL blood samples were obtained from each rat to determine inhibin B levels and contra lateral orchiectomies were performed in all groups to microscopically investigate electron. Inhibin B levels decreased in groups 3 and 4. The difference between group 3 with groups 1 and 2 was significant (p = 0.003 and 0.02). Also the difference between group 4 with groups 1 and 2 was significant (p = 0.006 and 0.002) but the difference between group 3 and 4 was not significant (p = 0.08). In group III (orchiectomy) TEM showed a normal sperm morphology and normal disruption of different stages of the spermatogonial maturation. Debris and vacuolar changes were seen in sertoli cells. Morphology of leydig cells slightly modified and the dilated cisternae of the Smooth Endoplasmic Reticulum (SER) were observed in group IV( trauma) mitochondria with degenerated cristae and enlarged vacuole were observed.