CONTEXT: The laboratory test turnaround times (TATs) that exceed the expectations of clinicians who order those tests, the so-called outlier test reporting rates, may be responsible for perceptions of inadequate laboratory service. OBJECTIVE: To monitor outlier test reporting rates for emergency department stat potassium results and routine inpatient morning blood tests. DESIGN: In 2 different monitors, each conducted for 2 years, laboratory personnel in institutions enrolled in the College of American Pathologists (CAP) Q-Tracks program tracked the percentages of emergency department stat potassium results and/or the percentages of morning rounds routine test results that were reported later than self-imposed reporting deadlines. SETTING: A total of 291 hospitals participating in 2 CAP Q-Tracks monitors. RESULTS: Participants monitored 225,140 stat emergency department potassium TATs, of which 33,402 (14.8%) were outliers, and 1,055040 routine morning test reporting times, of which 123,554 (11.7%) were outliers. For both monitors, there was a significant (P <.05) downward trend in the outlier rates as the number of quarters in which participants submitted data increased. CONCLUSION: Outlier reporting rates for emergency department stat potassium and routine morning test results decreased during the 2-year period of continuous monitoring. The CAP Q-Tracks program provides an effective vehicle by which providers of laboratory services may improve the timeliness with which they deliver the results of laboratory tests.