An outline is given of the techniques that have been used for exposure of small and large experimental animals to tobacco smoke. The effects of tabacco smoke inhalation on a wide range of biological systems have been investigated, and some important published studies have been noted. Much early work on tobacco smoke was equivocal because of the unsatisfactory exposure techniques, and the poor quality of animals used. Exposure techniques, particularly for small animals, are improving and more recent publications indicate an increased awareness of the special problems of working with tobacco smoke. At this time, however, exposure techniques anty of different tobacco smokes are essentially at the mid-development stage.