Sequences of hepatitis B virus (HBV) precore regions from 7 patients with HBV and hepatitis C virus (HCV) dual infection and 2 with HBV, HCV, and hepatitis D virus (HDV) triple infection were analyzed. Two patients, 1 with only acute HBV infection and 1 with only chronic HBV infection, were also included for comparison. All patients had antibodies against HBV e antigen (anti-HBe) except 1 with chronic hepatitis B and C. No precore stop mutation at codon 28 (TGG to TAG mutation) was found in 21 cloned sequences from the 7 patients with HBV and HCV infection, nor in 11 cloned sequences from 2 patients with HBV, HCV, and HDV infection. However, mutations in other positions of the precore region were observed in 2 patients with hepatitis B and C. In both cases, precore sequences with mutations in different positions were obtained from the same serum sample. No mutations were observed in other positions of the precore region in the 2 patients with hepatitis B, C, and D. The presence of anti-HBe in these patients was probably due to the low level of HBV replication and not to the presence of the precore stop mutant.