We assessed the effect of in-hospital call on clinical performance and emotional state in seven medical interns. Clinical performance was evaluated through the use of actors who were trained to pose as patients seeking consultation because of specific medical complaints. The physician-patient interaction was scored according to predetermined criteria. There was no significant difference in interns' performance whether or not the preceding 24 hours had been spent on call. On a standardized questionnaire, interns reported significantly more fatigue and depression after call. We conclude that the major discernible effect of call is a deterioration of interns' feelings of well-being.