Two families of well-defined organic-inorganic nanocomposites have been synthesized either by attachment of an initiator as a capping self-assembled monolayer on a gold cluster onto which a macromolecule is grown in situ or by preformation of a defined polymer, followed by covalent or adsorptive attachment to a surface-capped metal cluster. The characteristics of these composites are compared in size and local organization. Possessing nanometer-sized gold clusters at the core and poly(N-acylethyl-enimine) chains radially or tangentially connected to the core, the resulting materials were characterized by TEM, GPC, W, IR, NMR, and XPS spectroscopies. Larger particles with narrower polydispersity were obtained by in situ growth of the polymer on a preformed metal cluster, with best results being attained with a mixture of brominated and nonbrominated thiols in which steric accessibility to the initiator sites is varied.