The results of studies on effects of the amount and type of oxirane, amount of catalyst and water, and temperature on the course of reactions taking place in the system N,N,N＇,N＇,N"-pentakis(hydroxymethyl)melamine (PHMM)-oxirane carried out in aqueous media are reported. Quantitative determination of the content of functional groups present in the system and of side products formed in reactions of oxirane with water, made it possible to analyze in detail the processes taking place in the system. (C) 2000 John Wiley & Sons, Inc.