Clinicians often need to know whether a new method of measurement is equivalent to an established one already in clinical use. This article reviews the methodology of a method-comparison study to assist the clinician with the conduct and evaluation of such studies. Temperature data from 1 subject are used to illustrate the procedures. Although one would not make decisions on the basis of the findings from 1 subject, the large number of paired measurements in the data set permits its use for illustrative purposes. Currently available software eliminates the need for tedious statistical computation but does not reduce the burden of understanding the concepts underlying a method-comparison study and accurate interpretation of the findings.