Recently there has been a proliferation of interactive tailored patient assessment (ITPA) tools. However, evidence of the reliability and validity of these instruments is often missing, which makes their value in research studies questionable. Because several of the common methods to evaluate instrument reliability and validity are not applicable to interactive tailored patient assessments, informatics researchers may benefit from some guidance on which methods of reliability and validity assessment they can appropriately use. This paper describes the main differences between interactive tailored patient assessments and assessment instruments based on psychometric, or classical test, theory; it summarizes the measurement techniques normally used to ascertain the validity and reliability of assessment instruments based on psychometric theory; it discusses which methods are appropriate for interactive tailored patient assessments and which are not; and finally, it illustrates the application of some of the feasible techniques with a case study that describes how the reliability and validity of the tailored symptom assessment instrument called Choice were evaluated.