Intrinsic motivation (IM) refers to engaging in an activity for the pleasure inherent in the activity. Objective: The present paper presents a tripartite model of IM consisting of IM to know (engaging in an activity to experience pleasure while learning and trying to understand something new), IM toward accomplishment (engaging in an activity for the pleasure experienced when attempting task mastery), and IM to experience stimulation (engaging in an activity for feelings of sensory pleasure). The Tripartite Model of IM posits that each type of IM can result from task, situational, and personality determinants and can lead to specific types of cognitive, affective, and behavioral outcomes. The purpose of this research was to test some predictions derived from this model. Method: Across four studies (Study 1: N=331; Study 2: N=113; Study 3: N=58; Study 4: N=135), the three types of IM as well as potential determinants and consequences were assessed. Results: Results revealed that experiencing one type of IM over the others depends in part on people's personality styles. Also, each type of IM was found to predict specific outcomes (i.e., affective states and behavioral choices). Conclusions: The implications of the Tripartite Model of IM for motivation research are discussed.