The effects of gamma irradiation on the structure and properties of hydroxyapatite/poly L-lactide (HAp/PLLA) biomaterial have been investigated. Effects of radiation on microstructure, degradation of polymer part and thermal stability of composite were determined by scanning electronic microscopy (SEM), gel permeation chromatography (GPC) and thermogravimetric analysis (TGA), respectively. Mechanical properties were obtained through mechanical strength and elasticity modulus. Presented results show that properties of HAp/PLLA decay with irradiation dose, but for doses required for sterilization, changes and damaging effects are acceptable.