Disruption of normal calcium homeostasis has been implicated in the development of cell injury by certain chemicals. Furthermore, calcium channel blockers, which may prevent such a disruption, were shown to protect against this type of cellular damage in some excitable and nonexcitable tissues. Therefore, the present work was designed to address the role of calcium in the pachytene cell death caused by ethylene glycol monomethyl ether (EGME) by investigating the effect of the calcium channel blockers, verapamil and diltiazem, on the pathogenesis of such lesions. Male F344 rats were treated with a single gavage dose of 200 or 300 mg EGME/kg. Other groups of rats were treated with the same doses of EGME in combination with one, two, three, or four doses of verapamil or diltiazem. Twenty-four hours after administration of EGME, the animals were sacrificed, and the left testis and epididymis were excised, fixed in Bouin's solution, embedded in paraffin, sectioned, and stained with PAS-H. The sections were evaluated "blind" and scored for the number of lesioned stage XIV tubules. At 200 mg/kg, EGME produced a moderately severe lesion as characterized by pachytene spermatocyte cell death in stage XIV semniferous tubules. Verapamil was protective against this lesion with the protection being directly proportional to the number of verapamil doses administered and was maximum in rats treated with three doses. At 300 mg/kg, EGME caused a severe lesion in the testis, and verapamil was not as effective in protecting against this lesion as against the low dose of EGME. In contrast, diltiazem was not as effective as verapamil at either dose of EGME. These studies show, for the first time, that verapamil protects rats against EGME-induced testicular toxicity.