The reactions of arylbiguanides with isatin and with 1-methylisatin gave 2-oxo-3-arylbiguanidylidene-indoles and 4-amino-6-arylamino-2-(1'-methyl-2'-oxo-3'-indolidene)-1, 2-dihydro-s-triazines, respectively. Analogously, N-amidino-O-alkylisoureas reacted with isatin and 1-methylisatin to afford 2-oxo-3-alkoxyamidinoamidinylidene-indoles and 4-amino-6-alkoxy-2-(1'-methyl-2'-oxo-3'-indolidene)-1, 2-dihydro-s-triazines, respectively. The structures of these compounds were discussed.