This paper examines the life-span approach to developmental psychology as it relates to teacher development research and presents some empirical results demonstrating the potential of the approach for increasing understanding of teacher development. Five assumptions of the life-span orientation as applied to the study of teacher development are discussed. Additionally, a typology of characteristics of life events is specified. Both assumptions and categories of the typology are viewed in relation to their implications for teacher development. Reported next, as an illustration of the value of the life-span approach, is a longitudinal exploratory study of preschool teachers enrolled in the 2-year Child Development Associate inservice education program. In October 1981, May 1982, and March 1983, 55 subjects were administered a battery of measures to assess the teacher-as-person, teacher-as-teacher, and teacher-as-teacher-as-person. Findings revealed differences between first- and second-year trainees; effects of teaching experience; variation across time on teacher-as-person variables; and significant relationships between teacher beliefs and personal characteristics. In conclusion, the design and results of the study are discussed with respect to the contribution that a life-span approach to teacher development may have on the study of inservice education. (RH)