Arteriosclerotic changes were induced in the internal spermatic artery of rams to determine whether there is a link between this condition and some pathological conditions of the testes, similar to those that cause infertility in men. Eight weeks after the induction of testicular ischaemia, blood plasma was collected simultaneously from the jugular and spermatic veins after an LH injection (10 micrograms) and assayed for testosterone. The rams were then castrated and sections of the testis, ductuli efferentes and spermatic cord were examined quantitatively and qualitatively. Vascular disturbance decreased the percentage of normal spermatogenic epithelium (P < 0.01) and the diameter of the seminiferous tubules (P < 0.001). These effects were accompanied by an increase in the percentage of the interstitial region within the testis (P < 0.05). Macrophages, lymphocytes and other inflammatory cells became numerous in the interstitium as damage to the seminiferous epithelium progressed. The most striking feature of the ischaemic testis was the focal damage of the spermatogenic epithelium, that is, sections of the same testis exhibited both normal and germ cell-depleted seminiferous tubules. Concentrations of testosterone in peripheral plasma were not significantly altered by either unilateral or bilateral testicular ischaemia; however, the concentration of testosterone was higher in the experimental spermatic vein than in the contralateral spermatic vein (P < 0.05) as was the ratio of LH:testosterone (P < 0.05). Unilateral vascular disturbance of the testis did not cause damage in the contralateral testis. The ductuli efferentes of these rams also showed structural changes as a result of vascular disturbance.(ABSTRACT TRUNCATED AT 250 WORDS)