The prevalence of hepatitis C virus (HCV) genotypes in Southern Brazil was studied in the plasma of 100 HCV-RNA-positive patients attended in Porto Alegre, South of Brazil. Reverse transcription-polymerase chain reaction (RT-PCR) products from the 5' noncoding region were double digested with RsaI-HaeIII and BstNI-HinfI and analyzed by restriction fragment length polymorphism (RFLP). Three genotypes (1, 2 and 3) were demonstrable, the most prevalent being HCV type 1 (55 of 100 patients, 55%), followed by HCV type 3 (37 of 100 patients, 37%) and HCV type 2 (8 of 100 patients, 8%). There was an unusual high prevalence of genotype 3, in contrast to the majority of published data from the Southeast region.