The presence of mutants of the precore region of the hepatitis B virus genome was investigated in French patients with fulminant hepatitis. Only one of the 10 subjects had a detectable mutation by direct sequencing. On the other hand, 2/10 and 3/10 had evidence of coinfection by hepatitis D virus and hepatitis C virus. These results indicate that the precore stop mutation at codon 28 is not a general condition in fulminant hepatitis B and might reflect epidemiological factors.