The purpose of this study was to examine the extent to which goal-based (ego- and task-orientation) or interest-based (personal and situational interest) motivators accounted for two forms of learning outcomes: in-class physical activity level and summative achievement in various physical education units. Middle school students (N=98, 6th, 7th, 8th grade) were randomly selected with parental permission from two middle schools. The schools were randomly selected from a pool of suburban middle schools in a major East Coast metropolitan area. The criteria for school selection included (a) similar curriculum (b) skill- and knowledge-based assessment, and (c) similar teaching staff and student demographics. Achievement goal orientations were measured using the 13-item (1=strongly disagree, 5=strongly agree) Task and Ego Orientation in Sport Questionnaire (TEOSQ), personal interest using a 15-activity survey (1=lowest, 7=highest interest), situational interest using the 24-item (1=strongly disagree, 5=strongly agree) Situational Interest Scale (SIS). Physical activity levels were measured using Yamax Digiwalker to record the number of steps (Steps) each participant took in each lesson. A validation with Polar heart rate monitor data showed an acceptable concurrent validity for the Digiwalker data with r ranging from .65 to .92. Learning achievement (Achievement) were measured using an aggregated average grade from the participants' skill tests and written exams. Data were collected in two randomly selected co-ed lessons in each of the units: Dance, Fitness Club, Volleyball, Fencing/Multi-game, and Gymnastics. For each unit data were grouped using quartile split into two sets: (a) high (n: 13 to 15) and low (n: 14 to 15) physically active students and (b) high (n: 14 to 19) and low (n: 13 to 18) achievers. MANOVA analyses were conducted to examine the differences between the group means in each data set. Comparisons between high and low physically active groups revealed that situational interest was the only motivator that differentiated high-active students from low-active students in all units but Fitness Club (F ranging from 9.07 to 73.88, p < .01). The analysis between high and low achievers showed that high achievers demonstrated higher ego- and task-orientations and higher personal interest in physical education than the low achievers (F ranging from 5.69 to 11.00, p < .04). The significance of the study is to have revealed the outcome specificity of the motivators, suggesting that different motivators may be effective for different learning outcomes. Physical educators should consider the motivator-outcome specificity when developing motivation strategies.Keyword(s): middle school issues, physical activity, student issues