The knowledge of interaction between a supervisor and doctoral students brings important consequences for research purposes, for supervisor´s evaluation, and for a feedback to a supervisor. In this paper we introduce a descriptive instrument, Inventory of Supervisor Activities, which makes it possible to rate the supervisor´s activities. The instrument concentrates on supervisor´s activities during interaction with a student in three phases of the doctoral studies: before enrolment of the student, during the study and after completion of the study. The system covers 100 activities, which are hierarchically organized, and which make it possible to obtain a rather complex portrayal of the interaction of the supervisor with the doctoral student.