The photochemistry and photopolymerization activity of three novel t-butylperester derivatives of fluorenone have been examined and compared with unsubstituted fluorenone and a tetra-t-butylperester of benzophenone. The longest wavelength absorption bands of all three derivatives are blue-shifted from that of fluorenone itself with a marked increase in the corresponding extinction coefficients, associated with the electron withdrawing effect of the peroxyester groups and a concurrent increase in the charge transfer content of the molecule due to substitution. The fluorescence quantum yields of the fluorenone derivatives are also greater than those of fluorenone in a range of solvent systems; this effect is associated with an increase in the degree of charge transfer content in the lowest excited singlet state. Photoreduction quantum yields are also higher in 2-propanol solvent, that for the bis-perester derivative being twice that of the monoperester. The presence of a tertiary amine (triethylamine) enhances the photoreduction quantum yields due to an increase in the probability of electron abstraction. Conventional micro-second flash photolysis in 2-propanol solution indicates that free radical formation occurs from an upper excited triplet n-re* state. Rates of photopolymerization in bulk poly(methyl methacrylate) on a percentage basis are also higher for the three perester derivatives with those for the monoesters being greater than for the bisperester. The latter is associated with a much higher probability of self termination reactions. The presence of methyldiethanolamine enhances the rate of photopolymerization with both fluorenone and the monoperester derivatives but reduces that with the 2-t-butylperester, 7-nitro and bisperester derivatives due to competitive termination reactions. The results are discussed on the basis of the photophysical data and subsequent spectroscopic analysis of the polymer samples by second-order derivative u.v. spectroscopy and fluorescence analysis, both of which are shown to be valuable methods for the determination of chromophoric initiator fragments.