https://www.selleckchem.com/products/nrd167.html Polychlorinated biphenyl (PCB) is considered one of the environmental pollutants. It is used as hydraulic coils in vacuum pumps, pesticides transformers, heat-exchange systems, capacitors and as additives in adhesive inks, paints, plastics, copying paper and sealants. Alpha lipoic acid (ALA) is an antioxidant substance normally present in mitochondria as a coenzyme. To evaluate the protective effect of ALA on PCB induced testicular toxicity. Twenty five adult male albino rats were used in this study. They were divided into four groups, a control group included 10 rats, group II rats received alpha lipoic acid 25mg/Kg /day orally for 30 days, group III rats received PCB 5mg /Kg/day orally for 30 days and group IV rats received both PCB and alpha lipoic acid at the same previous dose for 30 days. At the appropriate time, the specimens were taken and prepared for light and electron microscope study. LM examination revealed structural alterations in group III in the form of wide spaces between seminiferous tubules that contain homogeneous acidophilic substance, partial or complete detachment of the tubules from the basement membrane and total distorted irregular shaped tubules. Also dilated congested blood vessels were seen. EM examination of this group revealed Sertoli cells with cytoplasmic vacuolation and dilated rER. The basement membrane appeared as thick and irregular line under Sertoli and spermatogenic cells and it was interrupted in some points. Primary spermatocyte appeared shrunken while others revealed vacuoles in the cytoplasm and perinuclear dilatation. Leydig cells showed irregular vacuoles and swollen destroyed mitochondria. Amelioration of the previous histological changes could be detected in group IV. It could be concluded that alpha-lipoic acid has a protective effect against PCB induced testicular toxicity. It could be concluded that alpha-lipoic acid has a protective effect against PCB induced testic