Thirty dogs that showed signs of fear in response to fireworks participated in an open clinical trial to assess the potential value of dog-appeasing pheromone for the alleviation of their behavioural signs. The treatment was delivered continuously into the atmosphere of each dog's home with an electrically heated diffuser. At the baseline assessments, the owners identified the behavioural signs of fear that their dogs normally displayed in response to fireworks, rated their frequency and assessed the overall severity of their responses. These measures were repeated at the final assessment and the owners also rated the change in their dogs' responses. There were significant improvements in the owners' rating of nine of the 14 behavioural signs of fear that were examined, and in their ratings of the overall severity of the responses. The treatment was generally associated with a reduction in the intensity of fear but there were variations in the responses of individual dogs.