Acylation reactions under Schotten-Bauman condition depend largely on the pH of the reaction medium. When the pH of the reaction medium was 9.0-10.0, the acylation of 0.1 mol of hydroxyproline with 2.5 mol of palmitoyl chloride in an aqueous acetone medium gave O-palmitoyl hydroxyproline and palmitic acid. In another reaction at a pH of 10.5-13.0, a small portion of the formed O-palmitoyl hydroxyproline was converted into N,O-di-palmitoyl hydroxyproline which is only between the range of 4.79% to 10.78%. However, at more higher pH values, the N-acylation reaction competed with hydrolysis of the formed O-palmitoyl hydroxyproline to regenerate palmitic acid and L-hydroxyproline which resulted in the reduction of percentage of N,O-di-palmitoyl hydroxyproline of 9.00%.