The electron spin resonance spectra of Mn2+ in NaCl single crystals are investigated in detail. Seven different spectra (I, II, III1, III2, IV, V and VI) are observed. The spectra I–IV are the same as those observed by earlier workers, while the spectra V and VI are observed here for the first time. The local symmetry at the paramagnetic ion is orthorhombic for the spectra IV and V and tetragonal for the spectrum VI about the crystallographic  direction. The properties of the spectrum IV are explained in terms of an associated pair Mn2+: O22− with O22− molecular ion at the nearest neighbour anion site in the  direction with its internuclear axis in the (001) plane. The spectrum V is assigned to the associated pair Mn2+: O22− coupled with a nearby cation vacancy in the  direction and the spectrum VI to Mn2+ ion associated with OH− ion at the anion site in the  direction with a probable second neighbour cation vacancy. All the observed spectra are analysed in terms of the parameters of the usual spin-Hamiltonian.