BACKGROUND: The effect of magnesium sulphate on mechanically provoked vasospasm of the flap pedicle on porcine model was not studied yet. Positive effect of magnesium sulphate on vasospasm was proved in previous studies on rat. METHODS: The bilateral pedicled flaps based on the caudal superficial epigastric arteries were raised on 8 pigs. Flaps on the right side were the treatment group; flaps on the left side were the control group. The vasospasm was provoked by the tension applied on the pedicle in the axial direction using 160g weight. The blood perfusion of the flap was monitored using laser-Doppler. The duration of the vasospasm was defined as the time from the release of the tension until the blood flow began to rise. These times were detected using an automated computerized detection. In the treatment group, magnesium sulphate was given topically on the vessel; saline was used in the control group. RESULTS: The duration of the vasospasm in the treatment group was significantly shorter than in the control group (P = 0.024). CONCLUSION: Magnesium sulphate 10% shortened significantly the mechanically provoked vasospasm on caudal superficial epigastric flap in a porcine model. Further clinical studies are needed to prove the effect in humans.