The quantitative analysis of 2-keto- l-gulonic acid (2-KLG) produced by microbial fermentation is described. 2-KLG is separated from other aldonic and ketoaldonic acids by high-performance liquid chromatography on an Aminex anion exchange column with ammonium formate or potassium phosphate as the eluant. This is a rapid and simple method for routine analysis of a large number of samples generated by fermentation studies. Gas chromatography—mass spectrometry permits the qualitative and quantitative analysis of nanogram levels of 2-keto- l-gulonate in complex media and provides confirmation of the HPLC results. The methodologies presented are useful for the analysis of a number of aldonic and ketoaldonic acids.