1.The conditions were found for the condensation of 3-amino-s-triazole with cyanoacetic ester with formation of 7-amino-s-triazolo[1,5-a]pyrimidin-5(4H)-one.2.By the condensation of 5-n-alkyl-3-amino-s-triazoles with cyanoacetic ester and of 3-amino-s-triazole with n-alkylcyanoacetic esters the 2- and 6-alkyl homologs, respectively, of 7-amino-s-triazolo[1,5-a]pyrimidin-5(4H)-one were obtained.3.Some reactions of 7-amino-s-triazolo[1,5-a]pyrimidine derivatives were studied.4.7-Amino-s-triazolo[4,3-a]pyrimidin-5(8H)-one or 5-amino-s-triazolo[4,3-a]pyrimidin-7(8H)-one was synthesized.