The equilibrium spreading pressures (pi(e)) of monostearin, monopalmitin, monoolein, and distearin crystals sprinkled on aqueous solutions containing ethanol (0, 0.1, 0.5, 1.0, and 5.0 mol/liter) and glucose, fructose, and sucrose (0, 0.1, 0.5 mol/liter) were studied using the Wilhelmy plate method. The experiments were carried out over a temperature range of 5 to 40-degrees-C. The magnitude of pi(e) depends on the lipid, on temperature, and on subphase composition. Equilibrium spreading pressure changes linearly with the temperature. The magnitude and the slope sign of that change are dependent on the film and subphase compositions. Thermodynamic analysis of the spreading is consistent with the hypothesis that interactions between monolayer molecules and the solute in subphase exist. These processes must include the features of the crystal spreading, the monolayer structural characteristics, and the adjacent aqueous subphase.