Hepatic periportal thickening (HPT) detected by ultrasonography has been established as a reliable tool for measuring hepatic morbidity due to schistosomiasis. During ultrasonographic examination of patients with prolonged pyrexia, we frequently noticed minimal grades of HPT in patients without a history of schistosomiasis. This led to ultrasonographic studies of conditions other than schistosomiasis in which HPT may occur. Subjects included 460 patients with Schistosoma haematobium infection, 107 urban patients with prolonged pyrexia without previous exposure to schistosomiasis, and 288 healthy controls unexposed to schistosomiasis. Grade I HPT was more prevalent (P < 0.001) in patients with pyrexia (56.1%) than in those with S. haematobium (32.2%) and was more frequent (P < 0.001) in patients with S. haematobium than in controls (11.1%). Typhoid fever was the most common febrile illness causing HPT. Grade II lesions were rare in patients with pyrexia (2.8%) or schistosomiasis (0.9%). Grade III lesions were present in only one patient with S. haematobium. Mild grades of HPT can occur in infectious diseases other than schistosomiasis. Cellular infiltration in the portal tract from chronic infectious diseases can frequently give the ultrasonographic appearance of grade I HPT.