Recent studies on novel reactions of thioamides, thioureas, and related compounds with various radical-forming agents such as phenylazotriphenylmethane,N-nitrosoacetanilides, and aryldiazonium salts are reviewed. The aryl radicals are shown to add to the sulphur atom of the fragments NH—CS—R or NH—CS—NH forming the adduct radicals NH—Ċ(SAr)—R and NH—Ċ (SAr)—NH, respectively. This is proven by isolation of the reaction products and by ESR spectroscopy. The main pathways of the adduct-radicals' transformations are the following: (i) Cross-disproportionation with other radicals due to hydrogen abstraction from an NH group yielding theS-aryl derivatives of isothioamides and isothioureas. (ii) Cross-disproportionation due to hydrogen abstraction from an α-CH group affording keteneN,S-acetals. (iii) “Growth” with the formation of bis-formamidine sulfides and bis-imidosulfides. (iv) Oxidation by CuIIto isothiouronium salts. Some relations which permit to predict the reaction pathway depending on the properties of the parent compounds are formulated. The radical arylation of the aromatic thioamides and some thioureas is shown to be a facile preparative method for the synthesis of the correspondingS-arylisothioamides and -isothioureas. The mass spectrometric behavior of the aromatic thioamides has been studied. The main fragmentation and rearrangement pathways under electron impact have been determined.