Abstract: Endogenous nitric oxide promotes smooth-muscle relaxation and vasodilation in several tissues, including the uterus. Transdermal nitroglycerine, a nitric oxide donor, has shown potential in reducing uterine contractions during premature labour. In women with moderate-to-severe menstrual pain, nitroglycerine patches applied during the early days of the menstrual cycle provided rapid and satisfactory pain relief in most patients. Headache was the most commonly reported side effect. A randomized, double-blind, placebo-controlled study is underway to confirm these findings.