We describe the photoinduced flocculation of a nonaqueous dispersion of core-shell nanoparticles (diameter = 50 nm). The particles consist of a tightly cross-linked core composed of poly(butyl methacrylate-co-ethylene glycol dimethacrylate) and a lightly cross-linked shell of poly(butyl methacrylate-co-ethylene glycol dimethacrylate-co-methacrylic acid). After converting the acid groups in the shell to 1-phenylketo-2-octadecyl ester groups, the particles could be dispersed in cyclohexane, sterically stabilized by the alkyl substituents of these ester groups. Photocleavage of these substituents (lambda = 310 nm) regenerated the -COOH groups and led to slow aggregation of the destabilized particles. This system allowed us to study the process of particle aggregation kinetics in the absence of long-range electrostatic interaction by using a combination of static and dynamic laser light scattering. Our results show that there exist two stages in the aggregation process. Initially, several particles come into contact to form small, elongated clusters. Subsequently, these clusters undergo further aggregation to form larger aggregates characterized by a fractal dimension of 2.3. Our results indicate that aggregation in the second stage follows a reaction-limited cluster-cluster aggregation mechanism. We also found that the average radius of gyration during aggregation scaled with time with an exponent of 1.4+/-0.1, much higher than predicted and found in previous experiments.