PURPOSE: Few studies have examined whether bioengineering can improve fecal incontinence. This study designed to determine whether injection of porous polycaprolactone beads containing autologous myoblasts improves sphincter function in a dog model of fecal incontinence. METHODS: The anal sphincter of dogs was injured and the dogs were observed without and with (n = 5) the injection of porous polycaprolactone beads containing autologous myoblasts into the site of injury. Autologous myoblasts purified from the gastrocnemius muscles were transferred to the beads. Compound muscle action potentials (CMAP) of the pudendal nerve, anal sphincter pressure, and histopathology were determined 3 months after treatment. RESULTS: The amplitudes of the CMAP in the injured sphincter were significantly lower than those measured before injury (1.22 mV vs. 3.00 mV, P = 0.04). The amplitudes were not different between dogs with and without the injection of autologous myoblast beads (P = 0.49). Resting and squeezing pressures were higher in dogs treated with autologous myoblast beads (2.00 mmHg vs. 1.80 mmHg; 6.13 mmHg vs. 4.02 mmHg), although these differences were not significant in analyses of covariance adjusted for baseline values. The injection site was stained for smooth muscle actin, but showed evidence of foreign body inflammatory reactions. CONCLUSION: This was the first study to examine whether bioengineering could improve fecal incontinence. Although the results did not show definite evidence that injection of autologous myoblast beads improves sphincter function, we found that the dog model was suitable and reliable for studying the effects of a potential treatment modality for fecal incontinence.