t-Butylperoxy radical adds to fullerenes to form a number of stable fullerene mixed peroxides. The reaction follows the stepwise radical addition mechanism, and usually gives a mixture of products with different numbers of ^t-butylperoxo groups attached on the fullerene cage. Sequential para-addition on the hexagons is the dominant addition pattern. The peroxo groups and fullerene carbons around them exhibit facile reactivity towards various Lewis acids and nucleophiles. The fullerene peroxides can be easily separated by normal column chromatography. Single-crystal X-ray analysis confirmed the presence of peroxo groups. To cite this article L. Gan C.R. Chimie 9 (2006).