WHERE EXISTING REFERENCE COLLECTIONS DO NOT SATISFY THE NEED, POTENTIAL REFERENCE COLLECTION FORMS AND RELATED QUESTIONS ARE DISCUSSED IN SOME DETAIL. RECOMMENDATIONS ARE PRESENTED TO GIVE DIRECTION AND STIMULUS FOR FURTHER INVESTIGATIONS INTO CERTAIN AREAS AND TO INDICATE THOSE AREAS WHERE NO ACTION APPEARS WARRANTED AT PRESENT. THIRTY-FOUR TYPES OF REFERENCE MATERIALS WERE IDENTIFIED AS BEING IN USE, OR AS BEING POTENTIALLY USEFUL REFERENCE COLLECTIONS. COLLECTION SPECIFICATIONS, MATERIAL SOURCES, COLLECTION IMPLEMENTATION FACTORS, USERS' FACTORS, AND RESEARCH REQUIREMENTS ARE DISCUSSED FOR EACH OF THESE TYPES OF MATERIALS. THESE 34 TYPES RUN THE GAMUT FROM HUMAN HAIR TO AUTO PAINT, FROM VOICE PRINTS TO SHOE PRINTS, AND FROM WOODS AND BARKS TO WATERMARKS. THE APPENDIX INCLUDES THE PERTINENT RESULTS OF FOUR SURVEYS OF FORENSIC SCIENTISTS AS TO THEIR NEEDS AND PRACTICES. APPROXIMATELY 140 REFERENCE CITATIONS ARE PROVIDED. (SNI ABSTRACT)