The semicontinuous surfactant-free synthesis of a core/shell sytrene/acrolein latex and its analysis for surface aldehyde functions are described. A colorimetric assay based on reaction with dinitrophenylhydrazine is compared with reduction by tritiated sodium borohydride and integration of aldehyde peaks in the proton NMR spectrum of the dissolved polymer. X-ray photoelectron spectroscopy confirmed the surface location of the aldehyde functions and the analytical reaction products. The three assay procedures were in reasonable agreement, suggesting all the aldehyde functions were accessible to aqueous reagents.