Temperature plays a primary role in seed germination, and germination under a wide range of temperatures can promote early seedling emergence and stand establishment. The objective of this growth chamber experiment was to determine the effects of temperature (5-35 degrees C) on the germination of eight species using 6 annual and 14 perennial cool-season grass lots. The greatest germination of annual and perennial cool-season grasses occurred at 20 and 15 degrees C, respectively. Germination of oat (Avena sativa L.) was typically greatest at 10 to 20 degrees C, whereas rye (Secale cereale L.) germination was generally greatest at 5 to 20 degrees C and annual ryegrass (Lolium multiflorum Lam.) germination was greatest at 10 to 30 degrees C. Germination of orchardgrass (Dactylis glomerata L.) and hardinggrass (Phalaris aquatica L.) was greatest at 15 to 20 degrees C. Germination of tall fescue [Schedonorus arundinaceus (Schreb.) Dumort.] varied by type: summer-active tall fescue had optimal germination between 15 and 25 degrees C but summer-dormant tall fescue had optimal germination between 10 and 20 degrees C, except for 'NFTF 1800E-', which was more sensitive to high temperatures (>5 degrees C). On the basis of these findings, the seeding rates of rye, oat, orchardgrass, hardinggrass, and tall fescue should be increased by similar to 30% if planted in early September rather than late September to account for the reduction in germination; summer-dormant tall fescue should be planted 2 to 3 wk later (1-15 October) than summer-active types (early September) in the southern Great Plains.