In most clinical trials, patients' mean improvement scores are compared either for active against active treatment or active against placebo treatment. Testing drugs or strategies to qualify as disease controlling antirheumatic therapy will require treated patients to satisfy set criteria. But what proportion must fulfill the requirement if the therapy is to be classified as DC-ART? While the answer must address the problems of semantics, disease characteristics, and absolute levels of improvement, it may be easiest to begin by defining a significant degree of change in terms of a single disease activity index.