A sense of efficacy, the extent to which teachers believe that they have the capacity to affect pupil performance, is related to both teaching behaviors and pupil performance. This study was designed to test the developmental hypothesis that teachers' sense of efficacy would increase during their successful progression through preservice training and inservice teaching. Approximately 300 outstanding preservice and inservice teachers at 4 distinctly different stages of career development were administered the Teacher Efficacy Scale. The sample consisted of highly successful teachers (N=225) and of high-potential prospective teachers (N=65) at the commencement of teacher preparation and at early-, mid-, and late career development stages. Findings indicated that the four groups of outstanding preservice and inservice teachers did not report statistically significant different senses of personal teaching efficacy or teaching efficacy. Differences between the 4 groups of responses of 5 of the 16 efficacy statements were significant, but the differences were limited to those between preservice and inservice teachers. These item analyses also indicated that preservice teachers tended to report a lower sense of personal efficacy but a higher sense of the efficacy of teachers as a group than did the inservice teachers. (Contains 16 references.) (LL)