A peristaltic pump smoking machine that allows simultaneous generation of mainstream (active) and sidestream (passive) smoke from a cigarette was used to expose cultures of murine L-929 cells, a potent producer of interferon, to smoke. The cigarette used was the University of Kentucky 2R1 reference cigarette. The dosages of smoke used for exposure were the highest doses possible that generated a minimum toxic effect, and they were serially diluted to lower doses. Dosages were determined by the number of smoke puffs generated, the volume of smoke puffs generated, and the total particulate matter deposited on Cambridge filters in the smoke machine. Viability of exposed cells was equivalent to control cell cultures. Interferon-alpha/beta was induced by addition of polyriboinosinic-polyribocytidylic acid to the cells. Interferon production was substantially reduced in viable cells exposed to mainstream or sidestream smoke. Aging of smoke by delaying time of exposure of the cells to the smoke, or filtration of smoke through activated charcoal substantially decreased the alteration of interferon production by smoke exposure. These results suggest that actual exposure of cells to mainstream or sidestream smoke can inhibit in vitro interferon-alpha/beta induction, but the cells can be protected from these effects by smoke manipulation.