Several papers and communications have reported possible weight reduction or less weight gain when patients start or switch to orally disintegrating olanzapine, as contrasted with standard oral olanzapine tablets. In this paper, the current literature is reviewed and hypothesized mechanisms of action are discussed. The data are still preliminary and mechanisms of action are not well understood. Randomized controlled trials are needed to further evaluate change in weight during treatment with orally disintegrating olanzapine. Copyright © 2008 John Wiley & Sons, Ltd.