Background: Interaction in medical consultations is of interest for many reasons and has long been thought an important variable in determining outcomes. Relatively few methods or instruments exist that attempt to access this phenomenon. The design, validation and possible application of a simple instrument to assess doctor-patient interaction are reported. Rapport and hostility may be related and we hypothesised that interaction between doctor and patient would be related in part to hostility. Methods: A simple instrument to assess doctor-patient interaction was designed based on 4 areas related to interaction and perception of’the other’. These were the areas of communication, rapport, trust and sense of ease. The instrument was compared with an external previously validated measure of hostility. Data were obtained from 74 women attending initial and follow-up consultations for chronic pelvic pain during the course of a larger study. Results: The instrument had acceptable reliability and a single-factor structure. Patients’ assessment of the initial consultation as unsatisfactory correlated with inwardly directed hostility (Spearman correlation coefficient, r = 0.30, p = 0.011). Patients’ tendency to rate the consultation worse than the doctor was correlated with inwardly directed hostility (r = 0.42, p Conclusions: This instrument offers a simple method of assessing some interactional aspects of a medical consultation.