This discussion departs from the usual presentation of experimental evidence, the results of original research, and subordinates experimental evidence to theory and perhaps to speculation.The subject is a very controversial one in the field of paint and varnish chemistry-how do oil-soluble metal salts accelerate the oxidation and polymerization of unsaturated triglycerides?In the last 10 years, much good work has been done on the chemical reactions involved in the drying of oils. Today, the gen-eral mechanism is fairly well accepted. The principal article in this discussion considers those chemical reactions involved in the drying of oils and proposes a mechanism to explain how oil-soluble metal compounds affect these reactions. Four experts in the field comment on and evaluate this proposal. This discussion is not expected to eliminate all controversy concerning drier action, but it is designed to spotlight areas of uncertainty and to point the way for future research.