This study examined the phenomena of the ownership of the classroom by a cooperating teacher and the constraints this imposes on the student teacher. Eight secondary language arts student interns completing a 14-week teaching internship participated in the study. Case studies were developed from data which included weekly unstructured interviews, bi-weekly journal accounts, two classroom observations, and structured interviews before and after the internship. Four facets of classroom ownership which formed distinct barriers for the intern teacher are identified and discussed: (1) the cooperating teacher's physical presence in the classroom; (2) the artifacts of teaching, e.g., the grade book, teacher's desk, building and room keys, and even the pupils considered as human artifacts whom the teacher "owns"; (3) length of the internship and interpersonal relationships; and (4) experience and decision making power. (JD)