The aim of this study was to examine the effects of threat appraisal (perceived susceptibility to re-injury or retarded rehabilitation and perceived severity of injury) and coping appraisal (self-efficacy, treatment efficacy and outcome value), in the framework of Protection Motivation Theory (PMT), on compliance to a sports physiotherapist's prescribed modalities and rest. During extensive developmental work, a Sports Injury Rehabilitation Beliefs Survey was constructed with 19 items to assess the PMT components. Five compliance measures were developed from physiotherapist and patient surveys. Data from 62 subjects (68% female, mean +/- S.D. age 21.7 +/- 2.85 years, and involved in many recreational and competitive activities) were obtained from a single university-based sports injury clinic, in a prospective study. The study revealed that over half the subjects were subsequently non-compliant to some degree. Greater perceptions of both susceptibility to retarded rehabilitation and injury severity, at the first appointment, were related to subsequent non-compliant behaviour. Greater self-efficacy in the ability to perform prescribed rehabilitation modalities, stronger beliefs in the treatment efficacy, and higher value attached to rehabilitation, were all related to compliant behaviour. Compliance to restricted activity (or rest) was only related to greater perceptions of susceptibility. The findings provide some support for PMT in this context and offer a basis for designing sports therapist interventions which focus on threat and coping appraisal.