Initiation of polymerization of a number of monometr molecules by the absorption of one photon is a form of chemical amplification. This process is started by system called "photoinitiation system" or "photoinitiator system". The photoinitiator system generates the free radicals that initiate radical chain polymerization of vinyl monomers. It may be a single compound that absorbs the light and then undergoes homolytic bond cleavage to form a pair of free radicals, or it may consist of several different compounds that undergo series of complex reactions to produce initiating radicals. This brief review summarizes a part of results obtained by members of our research group on the photochemistry and application of sulfur containing organic compounds used as photoinitiators and coinitiators of free radical polymerization.