1. PROCESS FOR PREPARING A STEROIDAL CYCLIC ACETAL WHICH COMPRISES REACTING A 16-HALOGEN-17-OXO STERIOD OF ANDROSTANE SERIES WITH A MEMBER SELECTED FROM THE GROUP CONSISTING OF REACTIVE THIO(LOWER)ALKANOIC ACID DERIVATIVES AND REACTIVE LOWER ALKYLDITHIOCARBONIC ACID DERIVATIVES, REDUCING THE RESULTING 16B-SUBSTITUTED THIO-17-OXO STERIOD OF ANDROSTANE SERIES WITH AN ALKALI METAL HYDRIDE COMPOUND AND CONDENSING THE RESULTANT 16B-MERCAPTO-17BHYDROXY STERIOD OF ANDROSTANE SERIES WITH A CARBONYL COMPOUND SELECTED FROM THE GROUP CONSISTING OF ALDEHYDES AND KETONES IN THE PRESENCE OF AN ACIDIC CATALYST OF ALDEHYDES THE 16B-MERCAPTO-17B-HYDROXY STERIOD 16, 17-CYCLIC ACETAL OF ANDROSTANE SERIES.