Scent-marking was studied in wolves (Canis lupus) along 133 km of tracks in northern Minnesota during winters of 1975 to 1976 and 1976 to 1977 and in two captive packs and four captive pairs for various periods. Lone wolves, which possess neither mates nor territories, rarely marked by raised-leg urination and defaecated and urinated less along roads and trails, where territorial pairs and packs generally marked. Newly formed pairs marked the most, eventually decreasing their rates to those of established packs. Generally, wolves that scent-marked also bred, whereas non-marking wolves usually did not breed. Scent-marking apparently is important to the success of courtship in new pairs and to reproductive synchrony in established pairs, as well as serving a territorial function.