2-Amino-4-chloro-5-formyl-6-[methyl(2-methylphenyl)amino]pyrimidine and 2-amino-4-chloro-5-formyl-6-[(2-methoxyphenyl)methylamino]pyrimidine are isostructural and form hydrogen-bonded sheets of R2(2)8 and R6(6)32 rings.