The extraction of HC104and HN03by N,N'-dimethyldioctyl malonamide (DMDOMA)an extractant of trivalent actinides from highly acidic solutions was investigated by distribution ratio measurements and IR spectroscopy. HCIO., is extracted as HDMD0MA+with an extraction constant of 4.15. HN03is extracted as HN03(DMDOMA)2,The extraction constant value for these species are respectively : The different behavior of HCIO,, and HN03has been attributed to their different acid strength, HC10-being a much more stronger acid than HN03.