Glutamine (Gln), which is the most abundant free amino acid in the circulation, and also a primary fuel for rapidly dividing cells, was used to determine its effects on incisional healing. The effect of Gin-enriched feeding was investigated using tensile strength measurement, which reflects the quality and speed of regeneration and by the measurement of tissue hydroxyproline line level which correlate directly with the collagen content of wounds. Forty albino Wistar rats in four equal groups received a special diet 7 days prior to surgery and 7 days after surgery. On the 7th day of study a 5-cm dorsal midline skin incision was made and then closed by interrupted sutures. Group 1 received a normal diet for all 14 days: group 2 received a Gln-enriched diet 7 days prior to surgery and a normal diet 7 days after surgery. group 3 received a normal diet prior to surgery and a Gin-enriched diet after surgery: group 4 received a constant Gin-enriched diet. On the 7th postoperative day, tensile strength measurements and hydroxyproline level analyses were done. A preoperative Gin-enriched diet did not show any significant improvement in the tensile strength and hydroxyproline levels on the 7th postoperative day, but a pre- and postoperative, and a postoperative Gin-enriched diet significantly improved the tensile strength and hydroxyproline levels when compared with the normal diet group (P<0.0001). These findings show that wound healing is better when Gin was added in the postoperative, or both pre- and postoperative periods, but not when only added in the preoperative period.