OBJECTIVE To investigate the expression and significance of peroxisome proliferator activated receptor γ(PPAR-γ) in human keloid. METHODS Twenty-three keloid samples were harvested from the patients undergoing keloid and auto-skin grafting operation as the experimental group (keloid group), and the residual normal skin after auto-skin grafting operation was collected as the control group. The expression of PPAR-γ protein was examined by immunohistochemistry staining in both keloid and normal skin. Referring to Shimizu immunohistochemical standard, the result was graded; the positive rate of samples and the rate of positive cells were calculated. RESULTS Immunohistochemistry staining showed that PPAR-γ protein was expressed in both keloid and normal skin. In keloid, it located in the pricle cell layer, and granular layer of epidermis, and the dermal vessel; the degree of dyeing was very light. However, in normal skin, it located in the base layer of epidermis, dermal vessel walls, sweat glands and sebaceous glands; the dyeing degree was deeper. Immunohistochemical staining score in the keloid group (2.65±0.78) was significantly lower than that in the control group (3.65±1.19) (t=5.030, P=0.000). The positive rate of samples in the keloid group (52.17%, 12/23) was significantly lower than that in the control group (82.61%, 19/23) (χ2=4.847, P=0.028). The rate of positive cells was 46.04%±8.61% in the keloid group, which was significantly lower than that in the control group (59.39%±11.26%) (t=5.974, P=0.000). CONCLUSIONS Compared with normal skin, the expression of PPAR-γ protein in keloid is down-regulated in in human keloid, indicating that PPAR-γ may be related to the formation of keloid.