To mate, natural Candida albicans a/α strains must undergo homozygosis to a/a or α/α, then switch from white to opaque. This is a more complex scenario than the mating process of S. cerevisiae, and involves a unique signaling process, in which mating-competent opaque cells, through release of mating pheromones, induce mating-incompetent white cells to become adhesive and cohesive, and to form a biofilm that facilitates mating. Induction of white cells involves the unique induction of white-specific genes by pheromone, mediated by a cis-acting sequence, WPRE, common to the promoters of white-specific, pheromone-induced genes. The configuration of the pheromone responses of white and opaque cells includes both common elements, the unique participation of the first intracellular loop of the common α-pheromone receptor in the white, but not opaque, response, and distinct downstream transcription activators. The evolution of this alternative pathway is discussed.