The U.S. Food and Drug Administration (FDA) Center for Drug Evaluation and Research is responsible for evaluating drug safety and efficacy, including oversight of clinical trials and principal investigators. The FDA Clinical Investigator Inspection List (CIIL) contains online, detailed, relevant information of all FDA inspections. We reviewed FDA inspections of clinical investigators to ascertain their outcome and included all inspections on the list (July 1977 through December 31, 2009; n ¼ 9,481 inspections). Eighty-eight percent of inspections were “data audit” (primary purpose ¼ verification of data), and the rest (12%) were “for cause.” The number of inspections each year significantly increased over time (P < 0.0001) and averaged 350 per year in the past decade. No deficiencies were found in only 11.2% of all “data audit” and 5% of all “for cause” inspections. Only 31% of inspections resulted in “no action indicated.” About two thirds of inspections resulted in some finding, requiring either voluntary investigator action (61.3% of inspections) or official FDA action (3.9%). The most frequently cited deficiencies were failure to follow investigational plan (34%), inadequate informed consent form (28%), and inadequate/inaccurate records (27%). In conclusion, over the past decade, the FDA has performed approximately 350 inspections per year, with the number increasing over time. The vast majority of FDA inspections yield deficiency findings and, as a result, only about one third of inspections have an outcome of “no action indicated.” Clin Cancer Res; 20(13); 3364–70. 2014 AACR.