We describe the synthesis and characterization of latex particles labeled with a brightly fluorescent yellow dye (HY) based on the benzothioxanthene ring structure. Three dye derivatives were synthesized with different spacers connecting the HY nucleus to a methacrylate group. For one of the dyes (HY2CMA, r(A)), we show that the reactivity ratios with styrene (r(A) = 0.71, r(B) = 0.25) and butyl methacrylate (r(A) = 0.87, r(B) = 0.14) should lead to random dye incorporation if the amount of dye in the feed is small. Seeded emulsion polymerization fails to lead to significant dye incorporation unless large amounts of nonionic surfactant are present. In contrast, miniemulSion polymerization worked well to yield latex particles of polystyrene, poly(butyl methacrylate), and poly(methyl methacrylate) with high monomer conversion and essentially quantitative dye incorporation. (C) 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 766-778, 2003.