Laboratory studies examining the effects of cigarette smoking on behaviour have routinely employed a variety of standardized smoking procedures. This study examined whether reaction time performance after smoking varied as a function of the cigarette smoking procedure employed. Twelve regular smokers were tested on a reaction time task after smoking on three different occasions. In each session, they smoked by one of the three following procedures: (1) ad libitum smoking of their own cigarette; (2) ad libitum smoking of a standard cigarette; (3) smoking a standard cigarette with a prescribed puff pattern. The results show that reaction time performance was significantly faster after smoking under the latter two conditions relative to the subjects' performance after ad libitum smoking of their own cigarette. These findings illustrate that experimental requirements which are commonly imposed upon subjects may affect the results obtained.