A 28-year-old Marine Corps officer developed Katayama fever with central nervous system (CNS) manifestations 6 weeks after swimming on Leyte Island in the Philippines. Symptoms consisted of fever, nausea and vomiting, focal visual field deficits and mild confusion. CAT-scan of the patient's head initially revealed multiple lucencies and severe edema in the left frontal, parietal and occipital lobes. No schistosome eggs were found in the patient's stool, and therefore he was treated with a 10-week course of dexamethasone with resolution of all symptoms over 3 months. Repeat CAT-scan after symptoms cleared showed complete resolution of the focal abnormalities seen earlier. The diagnosis was subsequently established by positive serology and by finding eggs in the patient's stool and in tissue obtained by liver biopsy. This is the first report of CAT-scan-detected focal CNS lesions in a patient with acute schistosomiasis japonica, and resolution of the CNS abnormalities, temporally related to non-specific steroid treatment, is documented as well.