The present invention relates to the oxidation with oxygen, or a gas containing it, of hydrocarbons to the corresponding carboxylic acids, alcohols and/or ketones or of alcohols and/or ketones to the corresponding carboxylic acids.More specifically, the invention consists of a process for oxidizing hydrocarbon, alcohol and/or ketone using oxygen or a gas containing it, in a liquid phase and in the presence of a catalyst dissolved in the reaction medium, characterized in that the catalyst comprises at least one soluble manganese and/or cobalt compound, at least one soluble chromium compound and at least one soluble iron compound.