Hepatitis C virus (HCV) genotypes were tested by the INNO-LIPA technique and the virus load determined by means of quantitative polymerase chain reaction (PCR) calibrated with standards using sera from 123 HCV patients. Of these 39 were on renal hemolysis treatment, 19 suffered from hemophilia, 13 were i.v. drug users and the remaining 52 had none of these risk factors (chronic hepatitis group). The most prevalent subtype in Austria was 1b, followed by 3a and 1a. However, genotype 1b infections were found relatively less often in hemophiliac patients and drug addicts than in the other two groups. This indicates that hemophiliacs probably had been infected by an antihemophilic plasma stemming from South American or Asian donors. The highest amounts of virus were found in patients infected with genotype 3a. Determination of the patient's virus load and of the infecting subtype may be helpful in planning interferon alpha therapy.