Vapor-liquid equilibrium and densities at 101.32 kPa have been determined for the binary systems formed by four butyl esters (from methanoate to butanoate) with ethanol. The four systems exhibit positive deviations from ideal behavior, and all data (p-T-x-y) were found to be thermodynamically consistent, The activity coefficients and the dimensionless function G(E)/RT of the solution were correlated with its concentration by different equations. An azeotrope was found in the mixture butyl methanoate (1) + ethanol (2) at T = 350.9 K and x(1) = y(1) = 0.088. The group contribution models ASOG and modified UNIFAC gave fair predictions.