This study was designed to throw light on the operation of 'planned activity time' (PAT) for teachers in Scottish schools. Five schools were selected for the investigation, two secondary and three primary, all in central Scotland, and 40 teachers were interviewed. Despite its origins in contractual compulsion, PAT has been surprisingly successful. In primary schools, whole-school activities associated with PAT, comprising 30 out of the required 50 hours, appear to be widely appreciated. The same is true of the 20 hours allocated to the development of courses in subject departments in secondary schools. In both cases the help that these activities gave teachers in implementing national initiatives in curriculum development was seen as of central importance. On the other hand, personal professional development, 20 hours of PAT, was broadly criticized by over 90 per cent interviewed and the 10 hours devoted to whole-school development in secondary schools were not valued by staff. In addition amongst secondary teachers there was a dislike of PAT because it was imposed on them. It was clear, however, that staff criticism could largely be dispelled if PAT was better managed. Thus personal professional development would be far more acceptable if staff views were taken into account in establishing a structure for staff development at school and local authority level, and if the scheme were properly evaluated. The unexpected conclusion of this investigation is that a modified form of PAT could well be acceptable to Scottish teachers, and to teachers in other countries, provided the compulsory element of PAT were clearly linked to an imperative recognized as important by teachers, for example the implementation of curriculum development at national level. Personal professional development would be more likely to be successful if detached from PAT and integrated into a well-resourced appraisal system that is sensitive to teachers' institutional and individual needs. Under certain conditions, therefore, the closer regulation of the non-teaching time of staff may be a viable option for governments and other employers of teachers in the future.