The University of British Columbia (UBC) Twin Project is a registry of approximately 1500 pairs of reared-together twins recruited from Vancouver, British Columbia and surrounding municipalities. The focus of the project is to examine personality and its disorders from a behavioral genetic perspective. The primary measures include self-report measures of variables from the major models of personality and personality disorders. Subsamples of the study have also been surveyed on a wide range of psychiatric conditions and symptoms, including, for example, substance use, mood, anxiety, coping, posttraumatic stress disorder, schizotypy, and several measures of the environment and experience. Also surveyed are general health and basic psychological processes including cognitive ability. This broad assessment has enabled us to examine not only the structure of personality, but also its potential role in psychopathology and other psychological processes. A feature of the project is that the measures selected reflect current thinking in the field as opposed to traditional psychiatric diagnostic criteria. The UBC Twin Project has been used in a number of collaborative projects on personality and psychopathology with other worldwide twin registries. At the present time, no DNA has been collected; however the facility to collect these data is available. Collaborative projects on this and future questionnaire studies are welcome.