The aim of this research was to study the germination conditions of two native forage species of the humid Argentine pampa prairie: Bothriochloa laguroides and Chaetotropis elongata. Mature inflorescences were obtained from Brandsen (Flooding Pampa sub-Region, Buenos Aires province, Argentina) from December 1995 to March 1996. A three-factor completely randomized design with four replications was used. Treatments combined prechilling, substrate moistened with KNO3 solution and germination temperatures: two constant (15 or 20ºC) and six alternating temperatures (15-10, 20-10, 20-15, 20-25, 20-30 or 20-35ºC in 16-8 hours) with ligth applied during eight hours. Time of afterripening applied (5-6 months) removed most dormancy. Prechilling and KNO3 enhanced germination response of the studied species, showing differential behaviour of seeds within the same population. High levels of normal seedling percentage were observed for 20-25ºC in both species.