The specific rate constants for the photofragmentation of four substituted benzene molecules (ethylbenzene, tert-butylbenzene, toluene, benzotrifluoride) following pulsed laser excitation at lambda = 193 nm were measured in a molecular beam experiment by monitoring the change of the intensity of the nascent products as a function of time delay between excitation and detection laser pulses. In the case of toluene (C6H5CH3), ethylbenzene (C6H5CH2CH3>, and tert-butylbenzene (C6H5C(CH3)(3)) a (3+1)REMPI process at lambda = 450.8 nm was used to ionize the CH3 products, which were detected in a time-of-flight mass spectrometer. Following dissociation of benzotrifluoride (C6H5CF3) the trifluormethyl radical CF3 was detected at lambda = 455 nm. The measured specific rate constants can be modeled satisfactorily by using the SACM (statistic adiabatic channel model) statistical theory.