Male mice produce pheromones that induce estrus in adult female mice. The synthesis of these chemosignals is controlled by testosterone. Male tissues abundant in testosterone-binding receptors were tested for their ability to stimulate estrus in grouped females. The percentage of females that showed estrus during two days following exposure to male tissues was used as the indicator of biological activity of tested samples. Homogenates of salivary glands and preputial glands induced estrus; other tested organs (liver, testes, coagulation and vesicular glands or kidneys) did not stimulate estrus in female mice. These results indicate that estrus-stimulating pheromone has multiple sources.