The present communication addresses the effect of chronic fluoride toxicity on the structure of rabbit Leydig cells using light, scanning and transmission electron microscopy. An ion-specific electrode method was used for the determination of fluoride in sera. The levels of fluoride in the sera of fluoride exposed rabbits were significantly increased (p<0.001) and in treated rabbits, transmission electron microscopy revealed dilatation of the smooth endoplasmic reticulum and mitochondrial cristae of the Leydig cells. Leydig cells with lower numbers of lipid droplets and smooth endoplasmic reticulum compared with Leydig cells of unexposed rabbits were seen. Some mitochondria were pyknotic whereas some revealed large electron-dense granules in their matrix. Intranuclear filamentous inclusions were also observed. The degeneration of the cytoplasm as seen using transmission electron microscopy is in agreement with the significant decrease (p<0.001) in the diameter of Leydig cell and nucleus as observed using light microscopy and with the degeneration of interstitial tissue of the testis observed using scanning electron microscopy. Thus, the extensive degenerative changes (which are progressive) seen in the Leydig cells due to fluoride toxicity may lead to a decrease in testosterone production resulting initially in regression of seminiferous tubules and structural damage of the epididymis and finally cessation of spermatogenesis.