The use of Gamma linolenic acid (GLA) and other essential fatty acid (EFA) metabolites in malignant cancer treatment in vitro and in vivo is briefly reviewed. Treatment of two dogs with multicentric lymphoma with large empirical daily doses of a combination of 40 mg gamma linolenic acid, 350 mg linoleic acid and 10 mg natural vitamin E per capsule resulted, after approximately one week, in slight to marked reduction in size of enlarged peripheral lymph nodes, spleen, skin nodules and tonsils. Both animals showed transient improved habitus and appetite, but deteriorated due to complications, apparently unrelated to therapy.