Fibre types and sizes and their relative numbers and cross-sectional areas in M. pectoralis, M. supracoracoideus, and M. iliotibialis of hand-reared and wild grey partridge (Perdix perdix) were determined in order to see if there are differences that could account for the poor survival of hand-reared birds released into the wild. Histochemical staining for myosin ATPase and succinate dehydrogenase (SDH) showed that most breast-muscle fibres (80-90%) are of the fast-twitch glycolytic (FG) type and a smaller portion of the fast-twitch oxidative glycolytic (FOG) type. In M. iliotibialis, about 60% of the fibres were FG fibres and the rest were of the FOG type. Judging from the low intensity of SDH staining, FOG fibres in the grey partridge appear weakly oxidative only. The relative number of FG fibres and their relative cross-sectional area in M. pectoralis were larger in the hand-reared than in the wild birds. The cross-sectional areas of both fibre types in M. iliotibialis were significantly larger in the hand-reared birds. Taken as a whole, these findings alone do not account for the poor survival of hand-reared partridge in the wild.