—Dr Rosenzweig's response indicates his failure to appreciate the scientific literature, the historical facts that led to CLIA, and the intent of our research.The Centers for Disease Control and Prevention has recently summarized all studies relevant to the issues addressed by CLIA.1 Of note was the lack of any solid evidence on the frequency of testing errors. Furthermore, this review found little evidence that the regulatory practices of proficiency testing, personnel licensure, and quality control have any relationship to the accuracy of testing of patient specimens. One study cited in this review did show that 93% of hospital laboratory errors were due to either preanalytic or postanalytic problems. It is ironic that such errors are barely addressed under CLIA, which instead deals primarily with analytic issues. There certainly is no compelling evidence that laboratory testing in the past or present is a serious public health issue.