Abstract Pyridine and 4-substituted pyrimidine derivatives incorporating a sulphur functional side-group were evaluated as potential radioprotective agents by screening tests in mice. 2- (2-Pyridyl) ethanethiol and its derivatives showed some radioprotective action when administered intraperitoneally, but all were inferior to 2-pyridinemethanethiol. They showed no protection when administered orally. Substitution of the pyridine ring by chlorine gave ...