The cycle of reproduction of Strombus gigas was established on the basis of samplings limited to 20 adults each month on the period of June 2006 to May 2007. After some preliminary essays conducted from November 2005 to January 2006, with fishermen practicing 40 m deep net fishing or fishing in apnea between 18 and 24 m, all the samplings were carried out by skin diving beyond 20 m in Guadeloupe. The harvested individuals had all a lip thickness of at least 6mm. The samplings during the fishing ban were carried out with a special authorization of the administration of fisheries of Guadeloupe. This study shows a reproduction cycle including a long period of rest that begins in October followed by a proliferation without differentiation in February. From March, gametogenesis is more precocious for males than for female conchs. Maturity begins for both sexes in May; it develops to a maximum from June to August and finishes in September by synchronous spawning. Partial spawns may occur only in August and September according to the presence of post spawn gonads at that time. It demonstrates that the fishing ban from February to September included is an absolute necessity to maintain a sustainable population of queen conch in Guadeloupe.