Abstract A dendrimer dye was prepared from a generation 2 polyamidoamine (PAMAM) dendrimer, which possesses 16 terminal amine groups. Reaction with 4-acetamidobenzene sulphonyl chloride yielded a fully substituted sulphonamide, as demonstrated by mass spectrometry and NMR. This was hydrolysed to the sulphanilamide hydrochloride, diazotised and coupled with 2-naphthol-3,6-disulphonic acid disodium salt, to yield an orange dye. The degree of substitution of chromophore units was ca. 85%, as determined by NMR and reductive titration. A pH 11 buffer was found suitable for gel permeation chromatography (GPC) analysis both of the initial dendrimer and of the dye product. GPC coupled with light scattering allowed molar masses to be determined.