In this note simple methods for the synthesis of several new fluorescent cell lineage tracers are described. These are fluorescent dextrans with average molecular weights of approximately 11 X 10(3), and with one or more fluorophore molecules covalently coupled to each dextran chain. These fluorescent dextrans are brighter than commercially obtainable products, and can be microinjected using either air-pressure injection or iontophoresis. They are long-lasting and have a uniform distribution in the cytoplasm of embryonic cells, clearly revealing very fine cell extensions such as cilia, axons, and filipodia. A method is also described for covalently attaching free amino groups to fluorescent dextran to make the tracers cofixable with cellular constituents by aldehyde treatment. Fluorescent dextran-amine tracers allow embryonic cell lineages to be studied in fixed, permeabilized, or sectioned embryos.