To obtain a ketal of steroid derivative as e.g. an intermediate for compounds useful for hormone administrative therapies for contraception, during and after menopause, by treating a 3-keto-steroiddiene derivative with an alcohol in the presence of a specific orthoester.

This ketal of steroid derivative expressed by formula IV is obtained by treating a 3-keto-5(10),9(11)-steroiddiene derivative of formul I [R1 is CH3 or C2H5; R2 is OH; R3 is H, CH3, C≡CH, CH2Hal (Hal is Cl, Br or I) or CH2CN, or R2 and R3 are combined into O] with an alcohol of the formula, HOR4OH (e.g. ethylene glycol) in the presence of orthoester(s) of formula II (R4 is a 2-5C alkylene) and/or formula III {e.g. 2,2-[1,2-ethanediylbis(oxy)]-bis-1,3- dioxolane} or their mixture.