The dehydration of butanediol-2,3 over activated Morden bentonite has been investigated. Below 350 °C., liquid products butanone-2, isobutyraldehyde, and the isobutyral of butanediol-2,3 were produced. Butanone-2 was obtained in 86% yield. At higher temperatures, 450° to 700 °C., gaseous decomposition occurred. Only small amounts of butadiene were formed from the dry glycol while a 25% diolefin yield resulted using water vapour as diluent. The decomposition of dry butanone-2 over bentonite gave only traces of butadiene. Yields of diolefin increased using water as diluent, 44.8% being obtained at 700 °C. with a ketone–water molar ratio of 1 to 40. Butanone-2 was considered intermediate in the formation of butadiene from butanediol-2,3.