Background:Carbon monoxide (CO) is a colorless, odorless, tasteless, and nonirritating gas which makes it difficult for those who are exposed, to detect it, leading to unexpected death. This study was undertaken to see the pattern of fatal CO poisoning and to discuss preventive aspect.Materials and Methods:It was a retrospective descriptive study of fatal CO cases which were autopsied at All India Institute of Medical Sciences, New Delhi, from the year 2010 to the year 2015. The cases were analyzed as per age groups, circumstances of death, season of death, and sources of CO formation.Results and Discussion:The study involved 40 cases of fatal CO poisoning. About 80% of cases were reported in winter months. The maximum cases were reported in the month of January followed by November and December. All the cases except one, died with a source of CO nearby and the person was inside a room or some closed space without ventilation. Source of CO was firepot and electric room heater in most of the cases. Some cases were of CO build inside the car with a running engine. Most of the cases occurred accidentally.Conclusion:Clustering of cases is seen in winters. Poisoning can occur in different ways. The study documents the various possibilities of CO poisoning and advocates community education targeting the high-risk groups and masses, especially during the winter season.