process for the concurrent preparation of olefinically unsaturated or satted α , ω - dialdehydes and α , ω - diacids , characterized by the fact that the monoozonide of a a mono - or polyunsaturated cycloolefine in solution in a polar solvent , is treated with water and subsequently with an alkaline aqueous solution at room pressure and at a temperature from - 5 ° c . to 70 ° c ., maintaining during the addition of the alkali , a ph not higher than 12 , the dialdehyde and the diacid being subsequently isolated by known , conventional methods .