A study was conducted to measure the extent of junior high school students' adjustment to physical education classes. Analysis was conducted on 459 male and 297 female junior high school students. First a scale to measure the extent was developed, which consisted of 14 items and two sub-categorized factors: "intention of solidarity," and "adjustment to physical education classes". The reliability was assured by Cronbach's a, corrected item-total correlation and the test-retest method,and the criterion-related validity was also supported by comparing the scale score with the physical competance test developed by Okazawa et al. (1996), with satisfying results for both. Next, based on the averages of the created measure's two sub-scales score, male and female junior high school students were classified respectively into the following four types of adjustment to physical education classes: the first type was named "solidarity-adjustment", the second type "peer interaction-mal-adjustment", the third type "avoiding unity-maladjustment", and the fourth type "at-one's-own-pace-adjustment". The psychological features of these types were considered by comparing their respective stress levels during physical education classes with the psychological stress response test developed by Sasaki (2000). The following results were obtained: 1) Male and female junior high school students who had adapted themselves to physical education classes comprised about 50% of the whole, respectively. Their lower stress response test scores suggested that they could tackle physical education classes substantiality. 2) On the other hand, there were also comparatively many male and female junior high school students who tended to avoid cooperative activity in their physical education classes. These students comprised about 30% of the total. Furthermore, their remarkably high stress level suggested that they had lapsed into lack of motivation to physical education classes. We then considered the problem of how physical education classes could be developed to accommodate this group.