OBJECTIVES As one of the factors related to doctor-shopping behaviour (i.e. consulting multiple doctors with regard to the same illness episode), very little has been revealed about the role of doctor explanation. We examined therefore the association between doctor explanation and doctor-shopping behaviour. METHODS The subjects were internist-patient pairs in Japan. Signal detection analysis (SDA) was used for the data analysis. RESULTS Of the 303 patients, 84 patients engaged in doctor shopping (27.7%). The following results were obtained: (1) of the 19 relevant variables, the 'level of doctor explanation: treatment' was the most significant predictor of doctor-shopping behaviour (P < 0.01), and (2) with regard to their subjective evaluations of the sufficiency of their explanations about treatment or testing, the evaluations of the doctors, rather than those of the patient, were significant predictors of doctor-shopping behaviour. CONCLUSIONS These results imply the following: (1) a patient's inability to understand a doctor's explanation about treatment, which results from a large gap between the perceptions of the patient and those of the doctor, is the most significant predictor of doctor-shopping behaviour, and (2) in the context of favourable patient-doctor interactions, when doctors feel their explanations are insufficient, they may be able to prevent doctor-shopping behaviour by providing relatively thorough explanations about treatment.