We report on recent results obtained for longitudinal field (T 1) spin relaxation of the muonium-substituted (“muonated”) free radicals MuCO, MuC2F4, MuC2H3F, and MuC4H8 (t-butyl), comparing with results reported earlier for MuC2H4 (and MuC2D4). Some comparison with transverse field (T 2) data is also given. These data are fit to a phenomenological model based on NMR theory of spin relaxation in gases. The parameters of these fits are presented and discussed.