The future of subject librarianship is being challenged by technological advances and funding pressures. Questionnaires were used to collect data about the roles, relationships and competencies of 32 subject/liaison librarians supporting three disciplines in UK universities. The survey showed that postholders were undertaking a wide range of activities, with academic liaison and information literacy teaching as central tasks. They had a variety of job titles and their roles demanded pedagogical and interpersonal abilities to complement their professional and technical skillsets. The study confirmed predictions of closer collaboration with academic colleagues and increased involvement in teaching. Communication is a key area, but formal mechanisms are less important than a proactive style and personal approach. Comparisons between diverse disciplines and institutional types found more similarities than differences, but revealed some distinctive features in the staffing and delivery of subject support for Law and differences of emphasis between old and new universities. (Contains 2 tables and 3 figures.)