Multiple hypothesis testing practices vary widely, without consensus on which are appropriate when. This paper provides an economic foundation for these practices designed to capture leading examples, such as regulatory approval on the basis of clinical trials. In studies of multiple treatments or sub-populations, adjustments may be appropriate depending on scale economies in the research production function, with control of classical notions of compound errors emerging in some but not all cases. In studies with multiple outcomes, indexing is appropriate and adjustments to test levels may be appropriate if the intended audience is heterogeneous. Data on actual costs in the drug approval process suggest both that some adjustment is warranted in that setting and that standard procedures may be overly conservative.