The medical records and magnetic resonance images of 33 dogs with surgically confirmed Hansen type I cervical intervertebral disc disease were reviewed. Fourteen of the dogs were chondrodystrophic and 19 were not chondrodystrophic. The most common clinical sign was neck pain, which affected 28 of the dogs, and 23 of the dogs were able to walk. Fifteen of the dogs had developed clinical signs acutely, within the previous 24 hours. On cross-sectional images the median area of spinal cord compression was 26 per cent (range 11 to 71 per cent) of the normal spinal cord area. The degree of spinal cord compression was significantly associated with the dogs' presurgical neurological status but not with their postsurgical neurological status. The dogs with an acute onset of clinical signs had more severe neurological dysfunction before surgery, but their condition improved more as a result of surgery.