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The reaction of diosgenin (1) with hydrogen peroxide/formic acid was investigated. As a result of this work, 5 α (25 R)-spirostane-3 β,5,6 β-triol (2) was prepared in 79% yield and 5 α-pregnane-3 β,5,6 β,16 β,20 α-pentol (3) in 80% yield. The pentol (3) was oxidised to 5 α-pregnane-3 β,5,10 β,20 α-tetrol-6-one (5) without forming its 16 β,20 α-isopropylidenedioxy derivative (4). Reaction of product 5 with CH3Mgl to give 6-methylpregnane derivative was unsuccessful. Therefore, product 7 was oxidatively degraded by H2O2/HCOOH to the 10-keto pregnane derivative (13) and its structure was proved through its transformation to 6 β-methylpregn-4-ene-6 α,20 α-diol-3,16-dione (15).