The periodate–permanganate oxidation of a terminal methylene group can be made to produce formaldehyde in high although not quantitative yield. Since the yields compare favorably with those obtained by ozonolysis, the reagent can serve as the basis for a convenient micromethod for the estimation of terminal methylene groups. The less than theoretical yields of formaldehyde are believed mainly due to the conversion of the olefin in part to α-hydroxyaldehyde in the initial stage of the reaction.