Experimental animal models need to be developed for studies of composite flaps that have often recently been used for defects of both bone and soft tissues. A consistent anatomy, simple surgical technique, and reliable blood flow are essential for the success of experimental flap studies. Here we propose a gluteus maximus-tensor fascia lata osteomuscle flap in rats as a model of these qualities. Gluteus maximus and tensor fascia lata muscles and the adjacent iliac bone segment were combined as a lateral circumflex femoral artery-based flap. To test the reliability of this composite flap, three types of composite tissues were harvested and replaced: osteomusculocutaneous flap, osteomuscle flap, and osteomuscle composite graft. The osteomusculocutaneous flap was elevated,by including a skin island over the gluteal region. The osteomuscle graft was formed by deliberately dividing the vascular pedicle of the osteomuscle flap. Direct observation revealed complete necrosis of the skin islands in all osteomusculocutaneous flaps. Microangiography of the flap demonstrated that both muscles and the attached bone were supplied by the pedicle. Dye studies with nitro blue tetrazolium (NBT) and India ink demonstrated dye uptake in both muscle and bone components in osteomuscle flaps. Histological examinations also demonstrated the viability of both tissues only in the flap group. Bone scintigraphy performed in flaps on postoperative day 7 demonstrated radionuclide uptake, confirming perfusion of the bony segment. The gluteus maximus-tensor fascia lata osteomuscle flap is a reliable and simple model for composite flap studies that offers the following advantages: 1) it is a new composite flap which includes bone, 2) it can be dissected easily with the naked eye, without using the microscope, 3) it has a long pedicle for flap displacement, and 4) it is a small animal model. (C) 2003 Wiley-Liss, Inc.