in furtherance of its exempt purposes of maintaining high standards in medical education and practice, encouraging research, and fostering measures for preventing disease and improving public health, publishes a monthly medical journal containing articles relevant to the practice of internal medicine. Each issue of the journal contains paid advertisements for pharmaceuticals, and medical supplies and equipment useful in the practice of internal medicine. After respondent had paid taxes on its net income from such advertisements in 1975, it filed a claim for a refund, and when the Government demurred, ultimately filed suit in the United States Claims Court, which held that the advertisements were not substantially related to respondent's tax-exempt purposes, and that therefore the advertising proceeds were taxable. The Court of Appeals reversed. Taking the view that the Claims Court had focused too much on the commercial character of the advertising business and not enough on the advertisements' contribution to the education of the medical journal's readers, the Court of Appeals held that respondent had established the requisite substantial relation and its entitlement to exemption from taxation.