The structured clinical interview for DSM-III personality disorders (SIDP) was the first semi-structured interview schedule developed to test and improve DSM-III Axis II validity and reliability. The SIDP-R is the revised edition for DSM-III-R. Both versions of this interview have been tested for reliability and validity, as well as presence and comorbidity of Axis II disorders. The validity of the SIDP has also been tested in a number of studies, usually in terms of concurrent/convergent validity with self-report questionnaires. The schedule for schizotypal personalities (SSP) provides information on SPD and achieves high reliability; however, it does not allow for determination of comorbidity with other Axis II disorders. One important feature is that the self-report measures of the schizotypal signs have been validated against clinicians' observation. The SSP also demonstrated strength specifically in the population it was designed on, that is relatives of schizophrenics, who constitute an important research group.