The critical temperatures and densities of the alkanoic acids containing up to ten carbon atoms have been measured using a sealed ampule method. Our critical temperature data show some disagreement with the data in the Literature, due partly to differences in the experimental techniques used and partly to differences in the extrapolation techniques employed to determine the true critical properties of the substances. No published data on critical densities of the alkanoic acids were available for comparison. The performance of several group contribution methods has also been examined and shown to be poor for the critical properties of the homologous series of alkanoic acids.