We investigated the expression of immunoreactivity (IR) for low- (p75) and high-affinity (trk proteins) neurotrophin-receptor proteins in adult human paravertebral-sympathetic ganglion neurons. Mouse monoclonal antibodies against the pan-neurotrophin-receptor p75, and rabbit polyclonal antibodies against specific epitopes of the intracytoplasmic domain on trk neurotrophin-receptor proteins were used in fresh unfixed and formaldehyde-fixed paraffin-embedded sympathetic ganglia. All adult human paravertebral-sympathetic neurons displayed trkA neurotrophin-receptor-like protein IR, 10% express trkC neurotrophin-receptor-like protein IR, 37-44% show p75 IR, and no IR was obtained for trkB neurotrophin-receptor-like protein. The intensity of immunostaining was independent of the neuron size. Labelling of non-neuronal tissues, especially blood-vessel walls, was observed for p75, trkA and trkC neurotrophin-receptor proteins. These results indicate that overlapping exists in the expression of p75 and trk neurotrophin-receptor proteins in adult human paravertebral-sympathetic neurons, and suggest that neurotrophins might act on these neurons.