AbstractBy the use of histochemical methods the enzyme acetylcholinesterase (AcChE) was visualized in nerve terminal appearing structures in the adventitia of small intramuscular arteries (30–100 μ) of cat and dog. These AcChE‐rich structures may represent cholinergir nerve terminals. Following chronic sympathectomy in dogs no AcChE‐rich nerve terminals were found in muscles on the operated side, indicating that these nerves represented sympathetic cholinergic innerva‐tion of skeletal muscle vessels, presumably the vasodilator nerves. In adjacent tissue sections of the muscle, adrenergic nerve terminals were histochemically visualized. Adrenergic nerve terminals were. seen in the same layer of the vessel wall as the cholinergic ones, i.e. in the adventitia surrounding the media. Adrenergic nerve terminals were found to innervate both large and small arteries. In muscle samples from monkey and human subjects no AcChE‐rich nerve terminals were observed around the vessels. However, adrenergic nerve terminals were found in these species with the same appearance as in cat and dog. This finding supports previous physiological experiments indicating that skeletal muscle of monkey lack sympathetic cholinergic vasodilator i