The influence of γ-irradiation on D – and L-glucose, D – and L-galactose, D – and L-mannose was examined in the solid polycrystalline state. Hydrogen was the principal gas product of radiolysis of hexoses. Radiation yield (G) of H2 changed from 2.2 for galactose to 3.2 (1/100 eV) for glucose and mannose. The ESR spectra of radicals formed in irradiated hexoses were similar and indicated the presence of secondary radical mixture. Integral G-value of radicals decreased with dose. Process of radical disappearance could be described with equations of polychronic kinetics. Radiation stability of galactose was one and a half times higher, than radiation stability of glucose and mannose. This fact rationalised essential contribution of the C4-H bond breaking process in formation of radical products and H2. Radiation stability of D – and L-isomers of monosaccharides under non-polarised irradiation was identical. Radicals formed in irradiated monosaccharides lived at room temperatures for several months and it should be taken into account on application of radiation-sterilized pills.