Equations have been derived from which long-range corrections to molecular simulation results for both uniform and nonuniform systems can be calculated. An important feature in the latter is the distortion of the singlet distribution function which is a consequence of the finite system necessary for simulation. The theory has been applied to the calculation of long-range corrections in a physical adsorption system (12-6 Ar on "homogeneous" graphite at 120 K ( T ∗ = 1.002 )). The results of these calculations, using an augmented summation procedure with large cut off, are compared with those previously obtained using a faster standard procedure with small cut off. The greatest discrepancy was found when appreciable coverages occurred at distances from the surface larger than the cut-off distance; however, satisfactory accuracy can be achieved with the faster procedure for coverages less than about two statistical monolayers and no major modification to previous conclusions was found to be necessary.