Patient characteristics William Stones, University of Southampton 19 August 2004 This paper prompted me to follow up the question of whether the patients in the studies reviewed were allowed to take the combined oral contraceptive pill. This is not mentioned as a specific exclusion criterion in the published papers. Dr Sahin (reference 13) was kind enough to confirm that pill users were indeed excluded. A response is not forthcoming so far from the corresponding author for reference 9.Thus it seems to be a completely open question as to whether rofecoxib is effective for women using the combined oral contraceptive pill. This is rather extraordinary given that so many do use the pill in order to reduce dysmenorrhoea.Two other points came up during my search of the Vioxx licensing documentation on the FDA website. Firstly, it is reassuring to note that rofecoxib had no effect on metabolism of the oral contraceptive pill- in contrast to valdecoxib which does seem to have some effect, albeit of uncertain clinical signficance. This is probably not so important in real life as pill users would typically be in their pill-free week while using analgesia for some days of the withdrawal bleed.Secondly and more importantly, none of the studies have included participants under the age of 18. Thus we are at a loss as to how to advise younger women with dysmenorrhoea - who must represent at least a third of the population at risk of primary dysmenorrhoea- regarding rofecoxib.One might wish that investigators would focus more closely on these important sub-groups of women with dysmenorrhoea, and not just do the 'easy' trials! Competing interests None to declare.