A multidisciplinary team which included two experts in the field of sexual assault developed a data schedule for investigative inquiry and offender assessment. This instrument provided not only guidelines for interviewing subjects but also a system of recording and coding relevant data to permit computer analysis and retrieval. The protocol is divided into five sections: (1) physical characteristics of the offender; (2) background development, (3) offense data, (4) victim data, and (5) crime scene data. The schedule was then administered to 3 groups of sexual offenders: 26 sex murderers, 125 rapists and child molesters, and 100 sex offenders confined to a mental health facility. The reliability and validity of the data will ultimately be tested by the accuracy with which predoctrines (offender profiles) derived from this data pool are fulfilled. The criminal personality research program is designed to contribute to advances in the study of sexual homicide by establishing a national data bank from which reliable information can be retrieved. Current research emphasizes the rape-murderer but may expand to include a broader variety of felony crimes such as hostage taking and techniques to improve hostage negotiation. Photographs and one footnote are given.