Seven patients who developed a similar headache syndrome are described. They first developed severe, exploding headaches while swimming, and subsequently experienced less severe headaches during physical exertion. They also developed headaches during sexual activity, which were similar to the previous headaches brought on by swimming. Majority of them were women in their thirties or forties. These symptoms were gradually subsided with or without medication after several weeks or months. The possible pathogenesis of this headache syndrome is discussed.