Using the indirect immunohistochemical technique, neuropeptide Y as found in human ocular nerves. While limbal blood vessels were innervated and a few nerves were seen in the trabecular meshwork, the cornea proper contained no immunoreactive nerve fibers. Neuropeptide Y-like immunoreactive nerves supplied the iris dilator muscle and, to a lesser extent, the iris sphincter. Immunoreactive nerve fibers were present within the ciliary muscle and the ciliary processes. Neuropeptide Y-like immunoreactive choroidal nerve fibers were frequently associated with blood vessels. The apposition of immunoreactive nerve fibers and melanocytes occurred throughout the uvea. The distribution of neuropeptide Y-like immunoreactive nerves in the eye closely parallels the adrenergic innervation. Evidence linking neuropeptide Y to the ocular sympathetic innervation is discussed.