This paper gives binary equilibrium data for the miscible systems benzene-acetic acid, ethyl acetate-acetic acid, acetic acid-water, and for the partially immiscible system ethyl acetate-water. Different values of the end activity coefficients are obtained for ethyl acetate and water, depending on the method of calculation. Furthermore, it is shown that in the immiscible region the extrapolated van Laar relationship does not hold.