The photochemistry of anti-inflammatory drug desonide (De, 1) was studied in aerobic as well as in anaerobic condition with different irradiation wavelengths (254, 310 nm) in acetonitrile and 2-propanol. All photoproducts obtained were isolated and characterized on the basis of IR, ¹H-, ¹³C-NMR spectroscopy and elemental analysis study. The products were: 11β,21-dihydroxy-16α,17α-(1-methylethylidenedioxy)-1,5-cyclopregn-3-ene-2,20-dione 2 (254 nm), 11β-hydroxy-16α,17α-(1-methylethylidenedioxy)androsta-1,4-diene-3-one 3 (310 nm/2-propanol), 17β-hydroperoxy-11β-hydroxy-16α,17α-(1-methylethylidenedioxy)androsta-1,4-diene-3-one 4 (310 nm/O₂/2-propanol). Cyclohexadienone moiety in ring A and keto group at C₁₇ were found to be deeply modified by UV light therefore, loss of biological activity both during storage and in vivo can not be ruled out.