The trypsin digestion and bleaching technique, with PAS-haematoxylin or Sudan black staining, was used for demonstration of the architecture and organization of the myelinated nerves of the cat iris. The myelinated nerves enter the cat iris as several bundles in many places on the iris root. The ciliary part of the iris contains strongly-developed myelinated nerve bundles running radially or obliquely and having circular anastomoses. On division and intersection, the myelinated nerves dorm a finer plexus with a rhomboid mesh in the pupillary part. The myelinated nerves do not follow the iris vessels. They are arranged according to the course of the connective tissue fibres. The myelinated nerves of the cat iris were considered to be sensory.