A simple and straightforward method for forming polymer grafts oil glass and silicon surfaces using thiol-ene photopolymerizations is presented. A linear thiol-ene system composed of 1,6-hexanedithiol and triethylene glycol divinyl ether was photopolymerized over a silicon Surface functionalized with a thiol-terminated self-assembled monolayer (SAM). Although the grafted thiol-ene films are thin, ranging from 0.1 to 9.6 nm, the thickness is linearly related to the molecular weight of the polymer formed in the bulk. Thus, the thickness is tunable simply by controlling the polymerization conversion or the stoichiometric excess of one component. By lithographically patterning the SAM chemistry on the surface prior to polymerization, 5 mu m wide lines of grafted thiol-ene polymer were created. Thin, grafted acrylic films, from 0.5 to 1.7 nm in thickness, were formed by photopolymerizing tert-butyl acrylate with a small amount of thiol chain transfer agent to control chain length and facilitate radical transfer to the surface.