The overall smoking prevalence among male medical students between the years 1955 and 1988 in a medical college in South India was 39.51 per cent. The trends of smoking appeared to be in three phases. An initial phase comprising of a steady rise to a peak in the late sixties and seventies, followed by a plateau of the prevalence in the next ten years and ultimately a sharp fall in the last five years. Study based on a mailed-in questionnaire to ten batches of students selected randomly, to study the factors affecting initiation and quitting of smoking showed that the peak period of initiation seemed to be in the two years before and after joining the course. There was a significant relationship between the presence of a smoker in the family and picking up the habit. Conversely, no significant relationships were found with respect to quitting.