We synthesized novel fullerene derivatives with amino, carboxylic, and ethyl ester groups. The HIV reverse transcriptase (HIV-RT) inhibition activities of these derivatives were higher than those of nevirapine, a clinically used HIV-RT inhibitor. However, they were less effective than those of the tricarboxylic derivative previously reported by our group, and the numbers of carboxylic groups did not affect the HIV-RT inhibition activity. Some derivatives have HCV RNA polymerase (HCV-RP) inhibition activities as well. Further optimization of the structure of the fullerene derivatives is required.