We investigated the consistency of behaviour over repeated tests in dogs, Canis familiaris. Dogs were tested three times, with an average of 30 and 35 days between tests. The behavioural test used in the study included 10 subtests that exposed dogs to various situations, such as the appearance of an unfamiliar person, play, preylike objects, metallic noise and a suddenly appearing dummy. Studies using the same test with many dogs have revealed five specific personality traits, labelled Playfulness, Chase-proneness, Curiosity/Fearlessness, Sociability and Aggressiveness, and one higher-order, broader dimension, interpreted as a shyness–boldness continuum. We used these traits in the present study. We found significant correlations over the test series in all the specific traits as well as in the Boldness dimension. The magnitude of trait scores for Playfulness, Chase-proneness and Sociability, as well as for the Boldness dimension, was stable between tests. The scores for Aggressiveness and Curiosity/Fearlessness, however, differed between the first two tests: the intensity of behaviour related to fear and aggression decreased from test 1 to test 2, but the intensity of exploratory behaviour increased. This result indicates that these two traits in dogs are sensitive to novelty, although individual differences are also maintained in nonnovel situations. The results suggest that playful, social, exploratory, avoidant and aggressive behaviour in dogs is influenced by stable dispositions; i.e. personality traits, that seem to have been important during the evolution of the domestic dog