Abstract: Two primary flight muscles of Miniopterus schreibersi were studied using morphological and histochemical analysis. All animals were killed with an overdose of sodium pentabarbital administered intraperitoneally. Muscles were dissected free, cleaned of excess fasia, blotted dry and weighed. Their proximal and distal portions were mounted in gum tragacanth on cork, quick-frozen by immersionin isopentane cooled to about -160°C. Transverse serial sections (10-12 μm thickness) were obtained with a freezing cryostat sections from each muscle were stained with Nicotinamide Adenine Dinucleotide Tetrazolium Reductase (NADH-TR) to assess oxidative capacity. The method was used demonstate Succinate Dehydrogenase (SDH) activity. Sections of each muscle were stained using myosin Adenosine Triphosphatase (mATPase). Two fast twitch fiber types are histochemically identified in pectoralis muscles of M. schreibersi. These were classified as type IIa and b according to glycine-calcium-formalin preincubation staining protocol for myosin ATPase. The primary flight muscles, serratus ventalis included type I, IIa and b fibers. Type I fibers in serratus ventralis were highly oxidative as stained darkly for NADH-TR. All type IIa fibers exhibited relatively intense staining properties for NADH-TR and SDH suggesting a intermediate oxidative capacity. In M. schreibersi primary flight muscles, type IIb fibers were low oxidative as indicated by light reaction for NADH-TR. Fiber ratios of M.schreibersi for the pectoral muscle are fiber type IIa 87% and fiber type IIb 13%. Fiber ratios for serratus ventralis are fiber type I 14%, fiber type IIa 70% and fiber type IIb 16%.