Robenacoxib is a nonsteroidal anti-inflammatory drug and a selective cyclooxygenase (COX) -2 inhibitor, registered for treatment of osteoarthritis and post-operative pain in dogs. In a randomized cross over investigator-blinded trial with client-owned dogs diagnosed with a form of cancer, we compare treatment with robenacoxib versus carprofen. Adverse effects (AEs), pain and Quality of Life (QoL) are assessed to determine which drug is the better choice in palliative management of the canine cancer patient. In the pain study, dogs were treated 28 days with one NSAID, had a wash out period of 1 day and were treated 28 days with the other NSAID. Physical examination and blood analysis were performed during a clinic visit every two weeks and every week forms assessing AEs, pain and QoL were filled out by the owner. This research project report discusses results of the first four patients participating in this pain study. Results in this paper are blinded, because of continuation of the study. The first patient showed no differences between treatments and only mild AEs and changes in scores, which were most likely caused by the effects of radiation therapy. The second dog survived 6 weeks and showed a difference in the two periods of the pain study, which may have been an idiosyncratic reaction of the dog to the NSAID secondly used. The third dog survived 3 weeks, thus was only treated with one NSAID; AEs and poor scores were most likely caused by progression of the tumour. The fourth dog showed no differences between treatments; AEs and changes in scores were most likely related to other causes than treatment. Recruitment of patients and use of the forms are discussed and recommendations are given for the continuation of the pain study. Advisors/Committee Members: Kirpensteijn, Prof. Dr. J.K..