A study was designed to quantify ambivalent behaviour during social aggressive interactions in wolves. Agonistic interactions in a group of six European captive wolves, consisting of three males and three females, were analyzed for bared teeth, body posture and the position of ears, tongue, lips, legs and tail. The behavioural elements in each of these categories were assumed to be neutral or to signal dominance or submission. Wolves were considered to show ambivalence when dominant and submissive signs were observed simultaneously. More than 200 aggressive interactions were videotaped and parts of them were analyzed frame by frame. Results indicated that male wolves showed high levels of ambivalence (48%) and that this behavioural trait is not linked to a particular social status. Regarding specific body signals, tail position was the most reliable indicator of status, whereas bared teeth was not linked to a particular position in a dominance relationship. The possible application of these results to understanding aggression problems in dogs is briefly discussed. © 2006 Elsevier B.V. All rights reserved.