The role of familial environment in the spreading of hepatitis C virus (HCV) infection is not well established. We studied 1670 family members for 578 anti-HCV+ subjects enrolled in 8 centres distributed throughout Italy. The prevalence of anti-HCV positivity was significantly higher in spouses than in offspring (15.6% and 2.1% respectively; p < 0.01), with no difference between northern and central-southern regions of Italy. Anti-HCV positivity was found almost exclusively in adults; among offspring, during the first two decades of life, the prevalence of anti-HCV positivity was significantly lower than in subjects over 20 years old (0.6% vs 3.1%, respectively).