In this experiment, the ultrastructural effects of orally administered lead acetate on rat (Rattus rattus) spleen were studied. Rats weighing approximately 200-250 g were used in this experiment. They were divided into five groups, each one including five rats. Group I served as the normal control group while the others served as the experimental groups. The rats were exposed to oral administrations of lead acetate of 2.5 mg dissolved in 1 mL of drinking water per day. The administration lasted 96, 144, 336, and 432 h. The animals were anesthetized using chloroform inhalation and the peritoneum was stripped open and the spleen was removed and prepared for histological observation using a staining technique. Hypocellular white pulp, enlargement of venous sinusoids, clustering of heterochromatin in nucleus, vacuolation in the cytoplasm, swelling of mitochondria, and the distortion of rough endoplasmic reticulum cisterns were observed upon electron microscopic examination of the spleen tissue cells. These cytopathologic alterations indicate that lead acetate has some drastic toxicological effects on cellular structures.