Drug companies in the pharmaceutical industry utilized a marketing and sales strategy referred to as detailing. Detailing involved a company sending a salesperson to visit a doctor’s office and providing the doctor with a list of details about the drug being sold. In order to focus their marketing efforts, pharmaceutical companies purchased prescriber-identifying information from pharmacies to help determine which doctors were most likely to prescribe patients with the companies’ drugs. A Vermont statute prohibited pharmaceutical companies from, among other things, using prescriber-identifying information in their marketing practices. IMS Health Inc. (plaintiff) challenged the Vermont statute as an unconstitutional, content-based regulation of speech.