Conversion of oleic acid has been monitored with time for the reaction with glycerine to yield selectively 1-glycerol monooleate, using a slightly basic ultrastable Y-zeolite as catalyst. Various experiments at different temperatures, catalyst concentrations, and glycerine/oleic acid molar ratios have been carried out. Results show that no significant amount of triglyceride appears in the reaction mixture during the esterification process. An approximate pseudo-second-order kinetic model has been proposed and tested, showing that it reproduces the experimental results with a maximum 10% error.