probably lies somewhere between these extremes, closer to that asssociated with the point estimate. And what about the woman with lupus nephritis, whose plight, described in Part A of this two-part essay, prompted us to find that trial of adding plasmapheresis to a regimen of prednisone and cyclophosphamide? Unfortunately, although plasmapheresis did produce sharp declines in the substituted end-points of anti-dsDNA antibodies and cryoprecipitable immune complexes, the trial did not find any benefit from plasmapheresis in the clinically important measures of renal failure or mortality. When a careful statistical analysis of the emerging data suggested little hope of ever showing clinical benefit, the trial was stopped. Conclusion Having read the introduction to this series and the two articles on using articles about therapy, we hope that you are developing a sense of how to use the medical literature to resolve a treatment decision. First, define the problem clearly, and use one of a number of search strategies to obtain the best available evidence. Having found an article relevant to the therapeutic issue, assess the quality of the evidence. To the extent that the quality of the evidence is poor, any subsequent inference (and the clinical decision it generates) will be weakened. If the quality of the evidence is adequate, determine the range within which the true treatment effect likely falls. Then, consider the extent to which the results are generalizable to the patient at hand, and whether the outcomes that have been measured are important. If the generalizability is in