The ability of intraperitoneal injections of a retrograde neuronal tracer, Fluorogold, to label the entire population of sympathetic preganglionic neurones was tested with a double-labelling strategy. Animals were injected intraperitoneally (i.p.) with Fluorogold, while Fast Blue or subunit B of cholera toxin were injected into a peripheral autonomic ganglion or into the adrenal gland. Sympathetic preganglionic neurones were then examined for retrogradely transported tracers. In all cases, preganglionic neurones labelled with Fast Blue or cholera toxin also contained Fluorogold, indicating that i.p. injections of Fluorogold do reliably label the entire population of sympathetic preganglionic neurones.