Department of Chemistry, Nagarjuna University, Nagarjunanagar-522 510 Manuscript received 13 December 1993, revised 8 February 1994, accepted 29 March 1994 Kinetics of substitution of 2-chloropyrimidine and 2,4,6-trichloro-1,3,5-triazine with a variety of nucleophiles are reported. The reactivity pattern shows that the halogens flanked by two heterocyclic nitrogens in a ring are displaced with facility. The reactions with pyridine of 2,4,6-trichloropyrimidinP and 2,4,6-trichloro-1,3,5-triazine are routed through W cations formed in successive displacements which explain the overall displacement of halogens in these systems.