Methylation of 4-hydroxy-6-nitro- and of 4-hydroxy-3-methyl-6-nitro-cinnolines gives the N-1 and N-2 methyl derivatives not the O-methylnitronate. It is shown that 4-hydroxy-8-methyl-6-nitrocinnoline and 3-bromo-4-hydroxy-8-nitrocinnoline are methylated only at N-2 while 4-hydroxy-3-nitrocinnoline reacts only at N-1. Quaternisation of 4-amino-6-nitrocinnoline and of 4-methylthiocinnoline with methyl iodide yields a mixture of the corresponding 1- and 2-methylcinnolinium salts.