Peccaries (Pecari tajacu) were marked for identification in the field by the attachment of a polyethylene braided rope harness. The harness is a collar-like band which is held around the neck with an auxiliary strap behind the forelegs. Saflag or Armor-tite triangular color patches were attached to each side. A standard-size harness was fitted to each individual animal by tying the ends of the braided rope into a square knot and fastening a hog ring around the center of the knot. In 16 months of pen testing, harnesses were placed on eight captive animals. During this period the polyethylene braided rope remained in excellent condition, but the patch materials did show wear and fading. Between August 5, 1963, and February 23, 1964, harnesses were attached to 15 free-roaming peccaries. The color patch could readily be seen at 100 yards with 7x binoculars. In recent years several methods have been devised for marking big-game mammals. Many of these visible markers permit positive identification of individual animals and also have good durability. Progulske (1957) used a leather and plastic deer collar that was retained for as long as 16 months. Lightfoot and Maw (1963) devised a polyethylene braided rope collar with a large collar flap that permitted identification of individual animals. The collared peccary has proved to be a difficult animal to mark for field identification. Minnamon (1962) used ear markers made of polyethylene braided rope with some degree of success. Because the peccary has a short, thick neck, it has not been possible to use collars as markers. During a study of the seasonal movements and herd activities of the collared peccary in southern Arizona, I developed a harness marker which is both permanent and conspicuous. The harness is essentially a collar-like band which is held around the neck with an auxiliary strap behind the forelegs. This arrangement provided an opportunity to attach a triangular color patch on each side. The harness was constructed from segments of %-inch polyethylene braided rope fastened together with ?%-inch copper rivets. The ends of the rope segments were melted with a plastic sealing iron and flattened with a plier (Fig. 1). The color patch consisted of a swathe of Saflag (made by The Safety Flag Co. of America, Pawtucket, Rhode Island) or Armor-tite (made by Cooley, Inc., Pawtucket, Rhode Island) vinyl coated nylon fabric. Red, orange, yellow, blue, and white colors were used. The color swathes were wrapped around the side of the rope triangle and fastened with Pliobond glue (made by Goodyear Tire and Rubber Co., Akron, Ohio). The overlapped edges of the swathe were sewn together after the glue dried. Heavy-duty staples were used to secure the patch to the rope triangle. Different symbols were cut from patch materials and sewn to the color swathes before the gluing process. Harnesses were placed on adult peccaries only. A standard-size harness was fitted to each individual animal by tying the ends of the braided rope into a square knot and fastening a No. 1 hog ring around the center of the knot. The neck strap was also adjusted for smaller animals by making a loop in the braided rope and securing it with a hog ring. The harness was tested primarily on captive animals, with the intention of applying 1 Contribution of the Arizona Cooperative Research Unit: University of Arizona, Arizona Game and Fish Department, The Wildlife Management Institute, and the U. S. Bureau of Sport Fisheries and Wildlife, cooperating.