This paper reports the way different combinations of organic acids and tertiary amines work as catalysts in various polyurethane systems. The term ''delayed action'' is defined with examples of model reactions and commercially available polyurethane formulations. The effects on the reaction parameters in several foam systems and one elastomeric formulation will be presented. From amongst the broad range of amine catalysts we chose the following for our study: 33.3% solution of triethylene diamine in dipropylene glycol THANCAT(R) TD 33 A GRAPHICS methylazanorbornane as pure substance THANCAT(R) AN 10 or a 33.3% solution in dipropylene glycol GRAPHICS