University of Missouri—Columbia Although a developmental model of supervision for counseling trainees holds considerable intuitive appeal, there is little empirical evidence to support such a construct. The purpose of the present research was to examine differences in supervision across levels of counselors-in-training that might have implications for a developmental model of supervision. To this end, three separate studies were conducted over a 2-year period that empirically examined various aspects of supervision. Specifically, the investigations examined differences across three counselor trainee levels (beginning practicum, advanced practicum, and doctoral interns) with regard to (a) the interpersonal influence process between the supervisor and supervisee (Study 1), (b) trainees' perceptions of specific supervisor behaviors contributing to supervisory effectiveness (Study 2), and (c) trainees' perceptions of the most important or critical incidents that occur within supervision during a semester (Study 3). The combined results were congruent with a developmental model of supervision. Specifically, the results suggest that across trainee levels (a) variables related to the interpersonal influence process differ, (b) different types of supervisor behaviors appear to be effective at different levels of supervision, and (c) different types of critical incidents are reported within the supervision process. The implications of these results which support a developmental model of supervision are discussed as well as suggestions for future research.