A new cyanogenic glycoside isolated from pods of Acacia sieberiana var. woodii has been shown by chemical and spectroscopic methods to be (2S)-2- [(6-O-α-L-arabinopyranosyl-β-D-glucopyranosyl)oxy]-3-methylbut-3 enenitrile. Acid-catalysed hydrolysis ofthe glycoside afforded arabinose and proacacipetalin, and base-catalysed doublebond migration gave 2- [(6-O-cr-L-arabinopyranosyl-~-~-glucopyranosyl)oxy]-3-methylbut-2-enenitrile.