AbstractThe paper describes the application and limitations of magnetic methods to the problems of free‐radical chemistry (detection and quantitative investigation of the free‐radical state, relationships between structure and free‐radical formation, “distribution” of the unpaired electron, detection of mesomeric C, O, N, P, As, and Sn radicals, g‐factors, triplet states, and hyperfine structure). The problem of the diradical is described, and the paper closes with a discussion of the “Se