New vapor-liquid equilibrium data for the binary systems diethyl ketone + 2-pentanone, diethyl ketone + 3-pentanol and 2-pentanone + 3-pentanol and for the diethyl ketone + 2-pentanone + 3-pentanol ternary system are reported at 101.3 kPa. The data were found to be thermodynamically consistent according to the Van Ness-Byer-Gibbs method for the binary systems and according to the McDermott-Ellis method for the ternary one. The experimental results show that the diethyl ketone + 2-pentanone system is well represented by assuming ideal behavior. The other binary systems exhibit slight positive deviations from ideality, and no azeotrope is present. The VLE data have been correlated with the Wilson, UNIQUAC, and NRTL equations. The ternary system does not present an azeotrope and is well predicted from the binary interaction parameters.