The dehydration of butanediol-1,3 over activated Morden bentonite was investigated. At 250° to 350 °C., the organic liquid products consisted mainly of n-butyraldehyde, butene-3-ol-1, and the n-butyral of butanediol-1,3. Formaldehyde was dissolved in the liquid products and considerable carbon was deposited on the catalyst. The gaseous products consisted of propene and butadiene-1,3, the maximum butadiene yield being 29%. Butanediol-1,4, over the bentonite catalyst, was converted to tetrahydrofuran in almost theoretical yields at 250° to 300 °C. At higher temperatures, 400° to 500 °C., gaseous decomposition occurred, the main products being propene and formaldehyde. Only traces of butadiene-1,3 were formed from the dry glycol while an 8% diolefin yield resulted using water as diluent.