This study investigated William Schutz's three-dimensional theory of interpersonal behavior and compatibility (FIRO) to determine its validity as a group measure of compatibility. Data were collected from 248 students enrolled in a multi-section course in small group communications at a large midwestern university. Subjects self-selected themselves into 47 groups of no less than five and no more than seven and participated in five hours of introductory interaction. After this, they were asked to develop and present two exercises on group communication topics. Several instruments, including the FIRO-B instrument, were administered to the subjects. Results revealed that the methodology of computing group compatibility from equations that measure internal dyadic compatibilities was inefficient and inappropriate. After a reanalysis, findings suggest that even though a specific dyad in a group is compatible, the behavior and interaction of other group members may be an intervening factor causing a compatible dyad to be ineffective in the group context. The complexity of group interaction as well as the competition for attention among the group's many members may keep specific dyadic compatibilities from surfacing. Findings also suggest that defining group compatibility by measuring dyadic compatibility runs contrary to the notion of group synergy--that a group may be more than an additive function of its parts. Continued investigations into methodological issues to determine if compatibility is a useful discriminator in distinguishing effective from ineffective groups appear to be called for. (Eleven tables of data are included; 26 references are attached.) (KEH)