The nascent steps in the pyrolysis of the lignin components salicylaldehyde (o-HOC6H4CHO) and catechol (o-HOC6H4OH) were studied in a set of heated microreactors. The microreactors are small (roughly 1 mm ID X 3 cm long); transit times through the reactors are about 100 mu s. Temperatures in the microreactors can be as high as 1600 K, and pressures are typically a few hundred torr. The products of pyrolysis are identified by a combination of photoionization mass spectrometry, photoelectron photoion concidence mass spectroscopy, and matrix isolation infrared spectroscopy. The main pathway by which salicylaldehyde decomposes is a concerted fragmentation: o-HOC6H4CHO (+ M) -> H-2 + CO + CSH4=C=O (fulveneketene). At temperatures above 1300 K, fulveneketene loses CO to yield a mixture of HC = C C=C CH3, HC = C-CH2-C = CH, and HC = C-CH=C=CH2. These alkynes decompose to a mixture of radicals (HC = C-C = C-CH2 and HC = C-CH-C = CH) and H atoms. H-atom chain reactions convert salicylaldehyde to phenol: o-HOC6H4CHO + H C6H5OH + CO + H. Catechol has similar chemistry to salicylaldehyde. Electrocyclic fragmentation produces water and fulveneketene: o-HOC6H4OH (+ M) -> H2O + C5H4=C=O. These findings have implications for the pyrolysis of lignin itself.