Seeded emulsion polymerization is used to produce large quantities of shape anisotropic, amphoteric particles in a size range of about 1 mu m. Copolymer dicolloids (CDCs) containing pyridine groups are synthesized by swelling spherical, lightly cross-linked polystyrene seeds with a mixture of styrene and pH-responsive monomer 2-vinyl pyridine followed by secondary polymerization to contrast with their analogue homopolymer dicolloids (HDCs) where the swelling step is carried out with styrene alone. After the particles are coated with a nonionic surfactant to minimize van der Waals attractions, surface potentials and aggregation properties of dilute suspensions are studied as functions of p1-1 and ionic strength. Compared to HDCs, which remain stable at all pH values studied (3 < pH < 9) up to an ionic strength of 5 M, the CDC particles show amphoteric behavior with strong attractions under conditions where dipolar interactions are expected to dominate.