Measuring diagnostic performance is essential to identifying opportunities for improvement. In this study, researchers developed and evaluated two electronic clinical quality measures (eCQMs) to assess the quality of colorectal and lung cancer diagnosis. Each measure used data from the electronic health record (EHR) to identify abnormal test results, evidence of appropriate follow-up, and exclusions that signified unnecessary follow-up. The authors describe the measure testing results and outline the challenges in working with unstructured EHR data.