This paper presents 4 studies which were conducted for the purpose of constructing and validating a new measure of people’s motivation for environmental behaviors, namely the Motivation Toward the Environment Scale (MTES). The MTES consists of subscales that measure an individual’s level of intrinsic, extrinsic, and a motivation for environmental behaviors. These subscales correspond to the different forms of motivation identified by Deci and Ryan in their self-determination theory (SDT, 1985, 1991). Results from the first study supported the factor structure of the scale and revealed a satisfactory level of internal consistency. Consistent with the SDT, the more self-determined forms of motivation were associated with more positive responses on the related variables. Implications for the manner in which the public could be encouraged to do environmental behaviors are discussed.