BACKGROUND: Hypothermia is a common complication of anesthesia and surgery. Because maintenance of the body temperature is an important aspect of anesthesia management, various methods have been used to prevent its occurrence. Covering the patient's skin surface with cloth is believed to prevent intra-operative hypothermia. So, we evaluated the efficacy of covering the head and face with a towel and sheet. METHODS: Sixty patients for abdominal surgery were assigned randomly to a control group or a covered group. After the induction of anesthesia, all patients were covered with towels and sheets as usual. In covered group of patients, the head and face were covered fully. Core temperature was measured at the esophagus continuously and recorded at 15 min intervals for 90 min and then at 30 min intervals over 90-240 min. Room temperature was 23-24 degrees C. RESULTS: Esophageal temperature after 90 min in the covered group was higher than in the control group (P < 0.05). Hypothermia occurred after 45 min in the control group and after 90 min in the covered group. CONCLUSIONS: Covering the patient's head and face helps maintain intra-operative core temperature.