Copolymers of methyl methacrylate with acrylophenone, tert-butyl acrylophenone and p-chloroacrylophenone have been photolysed in benzene solution and the structures of the unsaturated end groups in the oligomeric products determined by n.m.r. It is shown that photodegradation takes place mainly by a Norrish Type I process, similar to that which occurs with methyl methacrylate-methyl vinyl ketone copolymers, but that there is a minor, non-classical Type II component which is most apparent in methyl methacrylate-p-butylacrylophenone.