Cell recognition during development of the nervous system involves specific interactions between neuronal cell surface molecules and their environment. Thus one type of neuron could carry on its surface a molecule which allows it to be distinguished from other types of neurons. We have tried to identify such specific components by comparing cell surfaces of cultured chick sympathetic (superior cervical ganglion) and parasympathetic (ciliary ganglion) neurons. Using metabolic labeling with (3H)-fucose or surface-labeling with the galactose oxidase-tritiated sodium borohydride method, we have identified a glycoprotein with an apparent molecular weight of 120 kD which is present on superior cervical ganglion neurons, but can barely be revealed on ciliary ganglion neurons. This molecule thus distinguishes two subsets of neurons and might therefore play a role in mediating specific interactions between the sympathetic neurons and their environment.