Detection of chemical carcinogens by means of the "rat liver foci bioassay".

The rat liver foci bioassay designed as short-term screening test system in vivo is a reliable procedure for the detection of the carcinogenic potential of chemicals. The use of tumor prestages as markers is favorable in many respects: 1. There is a convincing correlation between foci and tumors. 2. The sensitivity is by a factor of more than 1,000 higher compared to the chronic carcinogenicity study. 3. It is the only system available so far for detecting liver tumor promotors. 4. There is promising prospect that carcinogenic agents with extrahepatic target organs can be detected.