Analysis of 145 reports of adverse occurrences involving patients in a medical-surgical intensive care unite (ICU), during the yearts 1974 through 1978, disclosed 92 instances of human error and 53 cases of equipment malfunction. A peak occurrence of reported incidents was found between midnight and 1 AM. Harm occurred more frequently if the patient was unattended (72%) than attended (49%) during the incident. Mortality for patients with an incident report filed during their ICU admission (41%) was higher than for all ICU patients (21%). The importance of a well-structured incident-reporting program to minimize problems of human error and device malfunction is stressed.