The results of the study on the activity of amine modifiers for unsaturated polyester resins obtained by reaction of diethanolamine (3-azapentane-1,5-diol) and N-phenyl-2-aminoethanol with 2,4-dichloro-6-methoxy-1,3,5-triazine, 2-chloro-4,6-dimethoxy-1,3,5-triazine or with cyanuric chloride are presented. Effects of the type and amount of amine modifier as well as cobalt accelerator on gelation time and stability of the resins were investigated.