The combined gastrocnemius-soleus (G—S) muscle flap is a new research model for use in microvascular free tissue transfer in rats. Harvest of the combined G—S muscle flap is straightforward technically, and its increased size makes it particularly useful for biochemical and morphological study. A single G—S muscle complex accounts for approximately 1% of a rat's total body weight (261.67 ± 21.60 g). It can be used as a free muscle flap based on its large femoral pedicle (artery diameter, 0.9 ± 0.1 mm; vein diameter, 1.6 ± 0.1 mm). Eight G—S muscle flaps were harvested as free muscle flaps and transferred to a recipient femoral site. The flaps were explored 24 hours after revascularization and assessed for viability by visual inspection of the muscle and vascular pedicle, as well as by fluorescein injection. A survival rate of 100% (8 of 8) was noted at 24 hours. This flap is reliable, easily harvested, and provides additional muscle bulk for microvascular research.