OBJECTIVE: To explore the effects of recombinant human growth hormone (rHGH) on the survival of the mouse slender narrow pedicle flap and the expressions of vascular endothelial growth factor (VEGF) and classification determinant 34 (CD34). MATERIALS AND METHODS: A total of 20 BALB/c mice were randomly divided into the experimental group (n=10) and control group (n=10). The flaps were transplanted for mice in two groups respectively. 6 h after the operation, the mice in the experimental group were administrated with rHGH via local subcutaneous injection, while the mice in the control group were injected with the same amount of normal saline. The laser Doppler was used to measure the sub flap blood flow rates before the operation, and 3 days, 7 days and 14 days after the operation, respectively; the flap necrosis and survival areas of mice in two groups were measured respectively, and the survival rate of the flap was calculated 14 days after the operation. Afterwards, the flaps of mice in two groups were exfoliated and the shape and structure of flap tissues were tested by the hematoxylin-eosin (HE) staining. Reverse transcription-polymerase chain reaction (RT-PCR) and Western blot were used to test the levels of mRNA and protein of VEGF and CD34 in the flap tissues. RESULTS: The flaps of mice in the control group mainly exhibited the black or grayish-black and lost the elasticity with the hard texture, while those in the experimental group were ruddy in color with favorable elasticity. The survival rate of flaps of mice in the experimental group was significantly higher than that in the control group (83.61 +/- 12.56% vs. 46.25 +/- 9.70%) and the necrosis area of flaps of mice in the experimental group was significantly smaller than that in the control group (1.32 +/- 0.16 vs. 4.13 +/- 0.35, p < 0.05). There were no statistical differences in the blood flow rates of mouse flap both before the operation and three days after the operation between two groups (p > 0.05), while the blood flow rates of mouse flap both 7 days and 3 days after the operation in the experimental group were higher than those in the control group (p > 0.05). Compared with those in the control group, the levels of VEGF and CD34 were significantly increased, but the levels of the inflammatory factors of the interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) were significantly decreased (p < 0.05). CONCLUSIONS: rHGH plays an active role in the survival of the flap through promoting the angiogenesis and inhibiting inflammatory reaction.