Subjects included 24 experimental and clinical psychologists, 20 psychiatrists, 29 prosecuting attorneys, and 26 defense attorneys practicing in Ontario, Canada. Psychiatrists and clinical psychologists were rated by all groups as more valuable expert witnesses than were physicians and experimental psychologists. Both defense and prosecuting attorneys gave higher value ratings to psychiatrists than to clinical psychologists on fitness to stand trial and dangerousness issues. As expected, psychiatrists agreed with this assessment, while psychologists felt that testimony by clinical psychologists on fitness issues was as valuable as that of psychiatrists. On dangerousness, defense and prosecuting attorneys and psychologists rated testimony by psychiatrists and clinical psychologists as equally valuable, while psychiatrists rated testimony by clinical psychologists as equal in value to that of physicians. All subject groups rated physician testimony on these issues low. All groups except prosecuting attorneys rated experimental psychologists' testimony as more valuable on eyewitness identification than on dangerousness or fitness to stand trial. Only defense attorneys and experimental psychologist viewed experimental psychologists as more valuable than clinical psychologists on eyewitness issues. 3 tables and 24 references.