Abstract: The objective was to evaluate the concentrations of lactic and benzoic acids in milk during 6 h after collection. Ten composite milk samples from 10 healthy lactating dairy cows were collected. At 0-6 h after collection, milk samples were analyzed for the concentrations of lactic acid by titration method and for the concentrations of benzoic acid by high-performance liquid chromatography. Results revealed that average concentrations of lactic acid at 0 h were 129.6±7.0 mg dL-1 and the concentrations gradually increased during the 6 h post-collection period. At 6 h after collection, the concentrations were 158.9±4.3 mg dL-1. Similar results were also observed for benzoic acids. At 0 and 6 h after collection, average concentrations were 0.09±0.06 and 0.13±0.03 ppm, respectively. These results confirmed that lactic and benzoic acids were normally found in fresh milk and their concentrations were increased when the measurement time increased.