Good diagnoses require good diagnosticians: collecting and integrating the data.

The use of sets of diagnostic criteria and excellent structured clinical interviews will not result in data that is adequate for valid diagnoses or for dimensional measures if the rater collecting the data does not have adequate clinical skills. In the absence of biological measures or tests we are dependent on the rater's diagnostic and interviewing skills-both with subjects about themselves and with family informants asked to provide information about others. Best estimate diagnosticians (who usually have more experience and training) cannot compensate for inadequate or incorrect information and may even be misled by the information provided to them. In reviewing videotaped interviews sent by "trained" and "experienced" raters who were seeking "certification," approximately 40% of the raters were judged to have failed to conduct an adequate diagnostic evaluation. Principal Investigators should make every effort to assure that their diagnostic data is being collected by experienced and well-trained professional raters and that the raters' ongoing work is subjected to close supervision and review.