This study examined the reliability and cosmetic outcome of a Z-transposition flap with mucosal advancement for repairing partial thickness defects of the lower lip measuring less than 50% the lower lip length. Eleven patients treated in 2003 and 2004 were prospectively evaluated. All patients had undergone Moh's tumor excision and were referred for reconstruction. All defects measured less than 50% the lower lip length. Wound healing problems, cosmetic outcome, and flap reliability were evaluated at greater than 3 months postoperatively. All patients healed uneventfully with good cosmetic results and flap reliability. The Z-transposition flap is an acceptable alternative for reconstructing partial thickness defects of the lower lip.