Kinetics of chemical reactions between organic free radicals and cupric and cuprous compounds is described. Most of such reactions are redox reactions. They proceed via an intermediate transient complex between a radical and a copper compound. The spectra of transient complexes were determined by flash photolysis and by pulse radiolysis. The structure of complexes is a subject of conjecture. The measured second-order rate constants of radical reactions with copper compounds are 10⁵-10¹⁰ M^-1.s^-1. Examples of such reactions are presented.