Observations by trained observers using the Descriptive Observation Record of Individualized Instruction were compiled on 335 teachers, who also completed a self-report of the Individualization of Instruction Inventory. Both inventory results were then examined with the purpose of determining the relationship between self-reports of the teachers and reports made by the trained observers, with this relationship having implications for inservice programs. The teachers' group was composed of 200 academic, 86 vocational, and 49 special education teachers from 20 school districts located near Austin, Texas. Major findings showed that (1) teachers' self-reports yielded higher scores than observer recorded scores; (2) discrepancies between scores derived from teachers' self-reports and observer-reported scores increased as the degree of individualization of instruction, reflected from observations, decreased; (3) scores derived from teachers' self-reports varied in a systematic way from observer-reported scores, which permitted the conversion of teacher self-reports into scores that were reasonable predictors of observer reported scores; (4) teachers who were observed to be individualizing instruction more tended to have more realistic perceptions than did teachers who were observed to be individualizing instruction less, and (5) teachers who were from districts which had offered inservice education in individualization in instruction seemed more enthusiastic as evidenced by invitations to view materials and student work. (TA)