This article examines trends in antidumping and countervailing duty investigation petition filings in the United States during the most recent 21-year period. Petitions were filed on a wide variety of goods, but most frequently on intermediate goods; the steel and chemical industries were the industries which sought antidumping and/or countervailing duty relief most often. Petitions are increasingly being filed as joint antidumping and countervailing duty investigations and the countries from which U.S. industries have most frequently sought duty relief were China, the Republic of Korea, India, and Japan. A number of trends were driven by petitions that included China, although that influence has been declining recently. Several patterns were visible with respect to the timing of petitions; most were filed in the middle of the week, late in the month, and late in the quarter, but not necessarily late in the year. Two rule changes during this time period affected some of these petition filing patterns.