Abstract The acidic dehydration of 17α-ethynl-17β-hydroxysteroids ( 1–3) was investigated. On reaction with thionyl chloride, phosphorus oxychloride, and formic acid, the desired dehydration was accompanied by chlorination, Wagner-Meerwein rearrangement, and D-homoaromatic rearrangement. The structure of the product from the transformation of 17β-hydroxypregn-20-yne derivative ( 3) on reaction with formic acid was misjudged. It was regarded as a pregn-16-en-20-yne ( 10) instead of the actually rearranged D-homoaromatic compound ( 11). As a consequence, physical data corresponding to this latter structure have been cited in the literature as those of pregn-16-en-20-yne derivative ( 10). This confusion prompted us to prepare compounds of both types ( 4,9,10, and 11), the characterization of which is here described.