We have developed a polymerase chain reaction (PCR) assay which distinguish
es genotype F from the other genotypes of hepatitis B virus (HBV). The meth
od was used to characterize HBV strains isolated in urban areas of the Braz
ilian Amazon. DNA was amplified in 54 of a total of 78 HBsAg-positive serum
samples, using universal, non genotype-specific primers. Only 4 (7.4%) wer
e identified as genotype F by our genotype-specific PCR assay. This proport
ion is notably lower than that previously reported in Argentina, Venezuela,
Peru, and Central America.