The Sarbanes–Oxley (SOX) Act was passed in 2002 in response to various instances of corporate malfeasance. The Act, designed to protect investors, led to wide-ranging regulation over various actions of managers, auditors and investment analysts. Part of SOX, and the focus of this study, targeted the disclosure by firms of “pro forma” earnings, an alternate (from GAAP earnings), flexible and unaudited measure of firm performance. Specifically, SOX directed the Securities and Exchange Commission (SEC) to craft regulation which would reduce – (...) and preferably eliminate – any pro forma earnings disclosure which might be “misleading”. Examining earnings press releases over a 3-year period, this study addresses three questions. Were firms disclosing pro forma in a potentially misleading manner, what was the nature of this potentially misleading disclosure, and did SOX affect the disclosure practices? We find the following. In 2001 (prior to SOX), 53 firms – over 10% of all U.S. S&P 500 firms – were disclosing pro forma earnings in a potentially misleading manner. This was being done most commonly by using traditional GAAP terminology (e.g., “net income”) in the press release headline to describe what was later in the press release revealed to be a pro forma amount (i.e., “net income excluding special items”). By 2003 (subsequent to the SEC regulation), potentially misleading disclosure practices were seen in less than 1% of the earnings press releases of S&P 500 firms. This significant reduction suggests that managers, prior to the regulation, were either careless in their pro forma reporting practice, or were intentionally – and unethically – attempting to mislead investors. Either way, we conclude that the SEC regulation was both necessary and effective. (shrink)