Concerns have been raised over the high turnover rate for clinical investigators. Using the U.S. Food and Drug Administration's (FDA) Bioresearch Monitoring Information System database, we conducted an online survey to identify factors that affect principal investigators' (PIs) decisions to conduct only a single FDA-regulated drug trial. Of the 201 PIs who responded, 54.2% were classified as “one-and-done.” Among these investigators, 28.9% decided for personal reasons to not conduct another trial, and 44.4% were interested in conducting another trial, but no opportunities were available. Three categories of broad barriers were identified as generally burdensome or challenging by the majority of investigators: 1) workload balance (balancing trial implementation with other work obligations and opportunities) (63.8%); 2) time requirements (time to initiate and implement trial; investigator and staff time) (63.4%); and 3) data and safety reporting (56.5%). Additionally, 46.0% of investigators reported being generally unsatisfied with finance-related issues. These same top three barriers also affected investigators' decisions to no longer conduct FDA-regulated trials. Our findings illuminate three key aspects of investigator turnover. First, they confirm that investigator turnover occurs, as more than half of respondents were truly “one-and-done.” Second, because a large proportion of respondents wanted to conduct more FDA-regulated trials but lacked opportunities to do so, mechanisms that match interested investigators with research sponsors are needed. Third, by focusing on the barriers we identified that affected investigators' decisions to no longer conduct FDA-regulated trials, future efforts to reduce investigator turnover can target issues that matter the most to investigators.