Homogeneous photoinduced graft copolymerization of 4-vinyl pyridine (4-VP) onto ethyl cellulose (EC) in the presence of three photosensitizers such as 1-acetonaphthone (1-An), 2-acetonaph-thone (2-An), and biacetal (Bi) in benzene solution was extensively investigated. Ultraviolet (UV) irradiation in the range 310 to 460 nm was used. The U V spectra of the mentioned photosensitizers showed n-π*transitions. Grafting parameters such as grafting percentage (GP) and grafting efficiency (GE) were determined as functions of the irradiation time and the concentrations of monomer, substrate, and initiator. The IR spectrum of the EC-g-4-VP copolymer shows the appearance of new peaks between 1600 and 1690 cm-1indicating the presence of poly-4-vinyl pyridine (p-4-VP) grafted chains. The rate of copolymerization of 4-VP onto EC in the presence of 1-An, 2-An, and Bi was determined as 0.98% min-1, 0.88% min-1and 0.042% min-1, respectively.