The critical temperatures and densities of acetic acid-water mixtures have been measured using a sealed ampule method. The measurements for pure acetic acid were compared with data reported in the literature and were found to be in good agreement. It is shown that the critical temperatures of acetic acid-water mixtures increase with the addition of water, and that the critical temperature-composition behavior is linear in the composition range studied. The limiting slopes of the critical lines were obtained and compared with those calculated using the RKS equation of state with a binary interaction parameter.