During a period of 10 months, 69 Saudi Arabian patients (14 children and 55 adults) were diagnosed as having acute non-A, non-B, non-C (NA, B, C) hepatitis at King Khalid University Hospital, Riyadh, Saudi Arabia. Seven of the paediatric patients had anti-hepatitis E virus (HEV) immunoglobulin (Ig) M and anti-HEV Igc; 26 adults (47.3%) had anti-HEV IgM and 30 (54.5%) had anti HEV IgG. These results, together with the fact that none of the 40 patients with acute hepatitis A virus infection, none of the 24 with hepatitis B virus, and none of the 30 with acute hepatitis C virus, had anti-HEV IgM, indicates that HEV is an important aetiological agent of acute NA, B, C hepatitis in Saudi Arabia, and that there are still other unidentified agent(s) responsible for acute hepatitis in Saudi Arabia.