INTRODUCTION: Quantitative descriptions of fiber type organization in hind limb muscles are incomplete or rare.METHODS: Fiber morphometrics for both rat tibialis anterior (TA) muscles were measured in 3 dimensions.RESULTS: Slow oxidative fiber area and perimeter varied in all zones. Fast oxidative glycolytic fibers (FOG) were predominant in the mediolateral and posterior zones, and fast glycolytic fibers (FG) predominated in the anterior zone. The mean area of FOG and succinate dehydrogenase intermediate fibers was lowest in the anterior zone. Mean area of FG was highest in the proximal and distal parts of the muscle. The area and perimeter of fast fibers differed significantly between the right and left limbs in the medial zone. In the middle and lateral zones, they differed at the proximal and distal parts.CONCLUSIONS: This detailed analysis in a high resolution, 3-dimensional map provides an essential tool for understanding the structure and function of TA muscles.