The actual process of reading diagnosis and the effects of examiner/student interaction upon the diagnostic outcome were explored in this study. A testing session of approximately 50 minutes, conducted by a university professor to determine the reading problems of a nine-year-old boy, was videotaped. Applying an ethnomethodological model for discourse analysis to utterances generated during the testing event, the investigators were able to explore reading test discourse in terms of speech acts, moves, and exchanges and to compare portions of this discourse of the same testing event across time as well as with discourse generated during classroom lessons. Several categories of evidence for the interactional nature of the testing event emerged from the data. The set-up, the test event, and classroom discourse all differed in interaction patterns. The data supported the notion that the interaction of tester and student is negotiated during the testing event by both participants. Thus, while engaged in this test event the participants created as well as interpreted the context for their own behaviors. (MKM)