Context: Physicians' psychological characteristics may influence their communication styles and may thus interfere with patientcentred communication. Objective: Our aim was to test the hypothesis that, in interviews with a cancer patient and a relative, physicians with an "external" locus of control (LOC; who believe that life outcomes are controlled by external forces such as luck, fate or others) have a communication style different from that of physicians with an "internal" LOC (who believe that life outcomes are controlled by their own characteristics or actions). Design, setting, participants and intervention: Eighty-one voluntary physicians practising in the field of oncology were recorded while performing an actual and a simulated interview with a cancer patient and a relative. Main outcome measures: Physicians' communication skills were assessed using the Cancer Research Campaign Workshop Evaluation Manual. Physicians' LOC was assessed using the Rotter I-E scale. The communication skills of the upper and lower quartiles of physicians in respect of their scores on this scale were compared using Student's t test. Results: In actual interviews, physicians with an "external" LOC talked more to the relative (P=0.017) and used more utterances with an assessment function (P=0.010) than physicians with an "internal" LOC. In simulated interviews, physicians with an "external" LOC used less utterances that give premature information (P=0.031) and used more utterances with a supportive function, such as empathy and reassurance (P=0.029), than physicians with an "internal" LOC. Conclusion: These results provide evidence that physicians' LOC can influence their communication styles. Physicians' awareness of this influence constitutes a step towards a tailoring of their communication skills to every patient's and relative's concerns and needs and thus towards a patient-centred communication.