A serological survey for antibodies to hepatitis C virus (HCV), dengue viruses (DEN), West Nile virus (WN), and sindbis virus (SIN) was carried out in sera of selected groups of the population of the Islands of Mauritius (n = 449) and Rodrigues (n = 115), Indian Ocean. 8.3% of 564 sera were positive for anti-HCV. In Mauritius, 2.1% of sera of healthy individuals were found with anti-HCV. The highest prevalence was found in sexually transmitted disease (STD) patients and prison inmates with 46.2% and 43.8%, respectively. None of the sera from blood donors sampled from Rodrigues Island had anti-HCV. Antibodies to arboviruses were detected in sera of individuals from both islands. Anti-DEN IgG was detected in 3.8% of sera from Mauritius and 0.9% from Rodrigues. Anti-WN IgG was detected in 2.2% of sera from Mauritius and 0.9% from Rodrigues. All sera from Rodrigues were without anti-SIN IgG, 1.1% of those from Mauritius were positive. This suggests that arboviruses occur on these islands.