Irradiation of 3α, 5-cyclo-6-oxo-17β-acetoxy-5α-androstan-19-oic acid (1) in tertiary butyl alcohol yielded 4α-tert-butoxy-6, 6-dihydroxy-17β-acetoxy-5α-androstan-19-oic acid 6, 19-lactone (2) and 6-oxo-17β-acetoxyandrost-4-en-19-oic acid (3) in 50% and about 10% yields respectively. The former (2) was found to be formed by photochemical addition of tertiary butyl alcohol to the α, β-unsaturated ketone system in the latter (3). In connection with the mechanism of the above reaction, photolysis of 6-oxo-17β-acetoxy-5α-androstan-19-oic acid (9) in methanol and tertiary butyl alcohol is conducted to yield 5, 6-secocarboxylic acid derivatives (17, 19, 20, 21), and irradiation of methyl 3α, 5-cyclo-6-oxo-17β-acetoxy-5α-androstan-19-oate in tertiary butyl alcohol was also described yielding methyl 4α-tert-butoxy-6-oxo-17β-acetoxy-5α-androstan-19-oate (4) and methyl 6-oxo-17β-acetoxyandrost-4-en-19-oate (14).