The Betazoid phase or more commonly known as "the Phase" is a physiological phase that all Betazoid and half-Betazoid females enter during mid-life, similar to Human menopause. It is only during "the Phase" that a Betazoid female becomes fully sexual as the sex drive of the female in question quadruples or more. Some females engage in sexual relationships with any male available while others focus their attention on a single male who will later become her husband. In the event that a male spurns the female's advances, the female would be deeply offended and take the rejection personally. In some cases, the female's telepathic abilities are impeded by "the Phase".
At the beginning of her relationship with William T. Riker, Deanna Troi "warned" Will of "the Phase" although she did not tell him that her sex drive could increase by more than four times in case that frightened him.
Deanna Troi experienced symptoms that could be attributed to the Phase in 2369 after a telepathic link to Ambassador Ves Alkar caused her to artificially age. Troi displayed an overt sexual aggressiveness and even attempted to seduce several members of the Enterprise crew. (TNG: "Man of the People")