The amount of NSAID intake could be considered as a clinically relevant outcome measure in ankylosing spondylitis. The information should include at least the following: (1) the type of NSAID; (2) the dose; (3) the number of days taking NSAID during the period of interest. The objectives of this initiative were to propose both an NSAID equivalent score and a way of collecting and analysing this information in longitudinal clinical studies/trials. For the NSAID equivalent scoring system, the recommendations are (1) to refer to a scale in which 0 = no intake, 100 = 150 mg diclofenac, 1000 mg naproxen, 200 mg aceclofenac, 400 mg celecoxib, 600 mg etodolac, 90 mg etoricoxib, 200 mg flurbiprofen, 2400 mg ibuprofen, 150 mg indometacin, 200 mg ketoprofen, 15 mg meloxicam, 400 mg phenylbutazone, 20 mg piroxicam, 20 mg tenoxicam; (2) to present the results as mean daily intake by considering the number of days on which NSAID has been taken during a period of interest. This initiative should facilitate the conduct and analysis of clinical studies/trials.