The Integrated Developmental Model (IDM) of supervision builds upon previous models of counselor and psychotherapist development. The IDM incorporates aspects of both a mechanistic view, using the machine as metaphor, and an organismic view, using the organism as metaphor, of development in describing trainee development through three levels and into a fourth or integrated level. Generally speaking, techniques and assumptions consistent with a mechanistic or behavioral orientation appear within each level of development as skills, knowledge, etc. combine in an additive manner. The overall model in describing change between levels of development more closely follows an organismic growth or qualitative change model. The IDM describes a trainee's progression through the developmental levels in terms of three basic structures: motivation, self- and other awareness, and autonomy. This progression is assumed to proceed in a relatively orderly fashion through various domains of functioning relevant to professional activities in counseling and psychotherapy. Eight domains are identified as important to professional development: intervention skills assessment; assessment techniques; interpersonal assessment; client conceptualization; individual differences; theoretical orientation; treatment goals and plans; and professional ethics. The added specificity of the IDM should be helpful to researchers and practitioners in testing the validity of its constructs. (ABL)