The determination of two secondary lipid oxidation compounds (hexanal and pentane) in liquid infant foods using a headspace solid-phase microextraction gas chromatographic (HS-SPME-GC) method has been developed and validated. The HS-SPME analytical conditions (fibre position, equilibration and sampling times) were selected. The analytical parameters of the method (linearity: hexanal from 2.48 to 84.78 ng/g, pentane from 6.21 to 79.55 ng/g; precision: hexanal<br> 2.87%, pentane<br> 2.34<br>3.46%; recovery: hexanal<br> 106.60%, pentane<br> 95.39%; detection limit: hexanal<br> 3.63 ng and pentane<br> 4.2 ng) demonstrate the usefulness of the method. Once optimized, the method was applied to liquid infant foods based on milk and cereals, and to powdered adapted and follow-up milk-based infant formulas (IF), stored for four and seven months. In all cases the hexanal content was higher in IF than in milk-cereal based infant foods. No pentane was found in IF.