Seventy two heavy smokers were treated by means of either 6, 12 or 24 hours of sensory deprivation, or by 24 hours of social isolation. There was a significant linear trend relating time in confinement to reduction in mean post-treatment smoking rate. A measure of cigarette craving while confined did not predict treatment outcome. Craving while confined for 24 hours exhibited a cubic trend, indicating a diurnal rhythm. Differences between the two 24 hour conditions were nonsignificant, but suggested that social isolation may be therapeutically preferable to sensory deprivation.