Abstract: The present invention relates to a photoinitiator composition that can be used to initiate polymerization upon exposure to radiation. The said composition includes both a composition which yields cations upon exposure to actinic radiation, such as an iodonium borate initiator and a stabilizing amino agent. The amino agent is a secondary or tertiary amine having the general formula (VIII), a sterically arranged cyclic amine having the general formula (IX), or an amine consisting of groups that have the general formulas (VIII) and (IX) and that are interconnected. ##STR1## The compositions are particularly useful when used in conjunction with polyorganosiloxane monomers and when exposed to ultraviolet radiation.