Greater appreciation has recently emerged regarding the critical role played by explosive thermal decomposition reactions during pulsed laser ablation of organic polymers. Direct evidence supporting the mechanistic details of an actual reaction remains elusive, however. On the basis of secondary ion mass spectrometry (SIMS) measurements of ablated material deposited at a receptor surface, we map out the decomposition chemistry of a methacrylic copolymer, elucidating three ablation mechanisms : chain unzipping, chain cross-linking, and monomer fragmentation. We present a unifying perspective based upon the general conclusions of a number of recent mass spectroscopic analyses and offer a rather intriguing parallel between pulsed laser deposition and plasma polymerization.