Monte Carlo simulation results for interacting chains at zero and elevated pressures ace presented using a new simulation method. Both bulb and interfacial properties are investigated over a broad range of pressures and temperatures, thus covering high and low lattice fluid densities. The bulk simulation data are used to investigate the predictive capabilities of the Sanchez-Lacombe lattice fluid theory and an equation of state theory including nonrandom effects which are assessed using Guggenheim’s quasichemical approximation. The nonrandom mixing theory accurately predicts all available data even up to the lowest densities whereas the Sanchez-Lacombe theory overestimates moderate densities and completely fails at low densities. Interface profiles exhibit generally larger density variations for the systems including interactions in comparison to athermals, and the effect of pressure is concentrated in the system on the interface.