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The purposes of the present study were to determine cardinal development temperatures (minimum threshold [base] temperature Tb, optimal temperature To, and maximum threshold [ceiling] temperature Tu) and to identify a method for estimating with accuracy thermal requirements for the planting-emergence (E) stage of 11 forage grasses. One hundred and twenty (120) seeds of each species were planted in containers under controlled conditions in a completely randomized design with three replications at constant temperatures from 15 to 46 °C in the controlled environment chambers at the Instituto Nacional de Investigaciones Forestales Agrícolas y Pecuarias (INIFAP) in Guadalajara, Jalisco, México. Cardinal temperatures and thermal requirement were estimated through both bilinear method (MB) and curvilinear method (MC), and their fitness was evaluated by means of direct comparison with development values observed in the controlled environment and through the coefficient of variation of E length expressed as accumulated heat units (UCA). Results showed that MB was best for estimating Tb and To, while MC proved better for estimating Tu. Tb (°C), To (°C), Tu (°C) and UCA values for planting-emergence for each species were: Lolium perenne 9, 31, 41, 80; Festuca arundinacea 10, 31, 41, 78; Hyparrhenia rufa 12, 32, 42, 62; Eragrostis curvula 13, 32, 47, 40; Chloris gayana 13, 31, 47, 40; Melinis minutiflora 13, 31, 43, 50; Pennisetum clandestinum 12, 32, 43, 65; Brachiaria mutica 14, 32, 43, 57; Andropogon gayanus 12, 37, 48, 66; Cynodon dactylon 14, 29, 44, 48; Pennicetum ciliare 13, 30, 42, 61, respectively. [ABSTRACT FROM AUTHOR]