The polymerization of a self-assembled monolayer of (mercaptomethyl)styrene is monitored in situ with surface enhanced Raman spectroscopy. Chemisorption of this thiol-containing styrene involves the loss of the S-H bond. The vinyl stretching mode at 1625 cm(-1), which disappears during both azo- and photoinitiated surface polymerization, is used to follow the kinetics of the process. Laser desorption/Fourier-transform ion cyclotron resonance/mass spectrometry confirms the transformation of the initiated monomer into a nondesorbable species.