In this work the effects of the interactions between monoglycerides (monostearin, monopalmitin, and monoolein) and solutes in subphase (ethanol, glucose, and sucrose) on the monolayer stability have been studied. The destabilization of monoglyceride monolayers has been followed kinetically by observing changes in the film area with time at constant surface pressure, or by measuring the surface pressure decrease as a function of time when the area is kept constant, using a Langmuir-type film balance. Sugars or ethanol in subphase increase the instability of monolayers. Temperature and surface pressure exert a significant influence on the loss of film molecules. Existing relaxation mechanisms have been tested by comparing the experimental data with the predicted relationships between the loss of monolayer molecules and time. There is competition between the collapse and desorption mechanisms for monolayer destabilization as a function of the monoglyceride, subphase composition, temperature, and surface pressure.