In a hot-humid climate, comfort ventilation involving air movement over the skin of the human body is a prime consideration for thermal comfort. In developing countries with such a climate, the use of an air conditioner is not economically feasible by a majority of the population. Therefore, ceiling fan assisted cooling strategies hold significance. Fans increase the air movement inside rooms, thereby causing the layer of sweat over the occupant's body to evaporate. This paper aims to assess the evaporative cooling effect of a ceiling fan in a naturally ventilated house. The study was carried out in the hot-humid climate of Chennai City in India during the hottest part of the year. The criterion for evaluating the indoor thermal performance of this study is the difference in the standard effective temperature SET under conditions of still air and under conditions of using a ceiling fan at 2 m/s speed. Indoor air temperature changes under still air (0.1 m/s) were collected in four rooms of varying orientations (NW, NE, SW and SE) and with varying opening sizes for a 24 hour period. Using the software 'ASHRAE Thermal Comfort Standard Tool' developed by Environmental Analytics (Berkeley, CA) for ASHRAE, the difference in SET was calculated for these rooms and for eight conditions of opening sizes. Also, indoor comfort conditions, based on the five-point thermal discomfort scale, were recorded. It was found that the ceiling fans are most effective in enhancing comfort during the early morning hours. In addition, ceiling fans are consistent in providing thermal comfort when opening sizes are very small (5% - 25% of the floor area). They are most effective when opening sizes are of the order of 10% to 60% of the floor area. It was found that the NW orientated room had the least number of comfortable hours even in the presence of a ceiling fan.