The paper is an introduction to the Proceedings of the Intl. Symp. on Data Bases of Genotoxicity and Carcinogenicity and their Usefulness for Hazard Evaluations, held in Genova, Italy, January 1991. The purpose of the meeting was to review the present status of genotoxicity and carcinogenicity data bases, to analyze and discuss the current level of development of these data bases and to determine whether they are considered satisfactory for the assessment of chemical hazard. Discussed were the data bases of the International Agency for Research on Cancer (including the EPA/IARC Genetic Activity Profile Data Base), the EPA Gene-Tox Data Base, the data base of the National Cancer Institute/National Toxicology Program, the TD50 Carcinogenicity Data Base maintained by Lois Gold at Lawrence Berkeley Laboratory, and data base related activities such as SAR research, statistical analyses, and experimental studies.