Both microcapsules and matrix particles were formed by interfacial polycondensations of styrene-maleic anhydride (SMA) copolymers and polyamines in oil-in-water (o/w) suspension systems. The morphologies formed depended on composition, molecular weight and loading of the styrene-maleic anhydride copolymer, as well as on amine partitioning and on the rate of amine addition. The organic phase was comprised of mixtures of ethyl acetate (good solvent) and dodecyl acetate (non-solvent). Dodecyl acetate served both as co-solvent, and as a model compound for controlled release of insect sex pheromones. The dependence of the release characteristics of the particles on the morphology is discussed as well.