Four groups of 6 pigs each were given 5 x 10(5) to 3 x 10(6) sporocysts of a Georgia isolate of Sarcocystis suicanis. Only the 6 pigs given 3 x 10(6) sporocysts became acutely ill at postinoculation days (PID) 12 to 15, and 3 of the 6 diet at PIG 14 or 15. Clinical signs included purpura of the skin of the ear, snout, and buttocks and dyspnea, muscle tremors, and severe locomotor difficulties. Clinical abnormalities were accompanied by laboratory findings of pyrexia, severe anemia, leukopenia, thrombocytopenia, megathrombocytosis, prolonged prothrombin time and activated partial thromboplastin time, and hypofibrinogenemia. Seemingly, excessive intravascular coagulation may be involved in the pathogenesis of this disease in swine. Pigs given 5 x 10(5) to 1 x 10(6) sporocysts did not exhibit clinical signs; however, leukopenia and thrombocytopenia were demonstrated in the pigs at all dosage levels. Growth rates were impaired in surviving pigs. Second-generation schizonts containing merozoites were found in vascular endothelium of pigs dying on PID 14 or 15. Nonsuppurative myocarditis and hepatitis were present. Numerous developing cysts were in the musculature of pigs enthanatized on PIG 35 to 52. Cyst dissolution and resorption occurred concomitantly, indicating that swine may be able to clear the infection.