Induction of regeneration and maturation of the free-living gametophytes of Undariopsis peterseniana (Kjellman) Miyabe et Okamura was studied at four temperatures (5, 10, 15, and $20^{circ}C$), four levels of irradiance (5, 10, 20, and 40 ${mu}mol$ $m^{-2};s^{-1}$) and three photoperiods (14:10, 12:12, and 10:14 h L:D). Female gametophyte fragments were maintained in active regeneration without reaching sexual maturity under conditions of $15^{circ}C$, 20 ${mu}mol;m^{-2};s^{-1}$, 10:14 h (L:D), whereas the conditions for male gametophytes were slightly different at $15^{circ}C$, 20 ${mu}mol;m^{-2};s^{-1}$, 14:10 h (L:D). The sexual maturation of female and male gametophytes took place under $15^{circ}C$, 20 ${mu}mol;m^{-2};s^{-1}$, 14:10 h (L:D) and $10^{circ}C$, 10 ${mu}mol;m^{-2};s^{-1}$, 10:14 h (L:D), respectively. These results provide basic information for controlling the regeneration and maturation of free-living gametophytes for artificial seed production of U. peterseniana.