Literature data of rate constants k(Delta)(Q) of electronic energy transfer (EET) from O-2((1)Delta(g)) singlet oxygen to 28 carotenoids have been analyzed by means of a semiempirical model derived for the deactivation of triplet excited (T-1) molecules by O-2((3)Sigma(g)(-)) triplet ground-state oxygen. The analysis demonstrates that EET from O-2((1)Delta(g)) to carotenoids occurs not via the electron exchange mechanism according to Dexter but principally via formation of (1)((1)Delta(.)S(0)) encounter complexes that deactivate irreversibly by internal conversion to (1)(T(1)(.3)Sigma) encounter complexes leading to formation of the T-1 excited carotenoid. The dependence of log(k(Delta)(Q)) on the excess energy of the EET process is quantitatively described. The results indicate that EET processes to and from O-2 could generally occur via IC of excited complexes.