It was found of interest to study the possible specificity of the test with other types of gkin carcinogens differing from those used in the first blind test. The 7,9-dimethyl-benz-(c)-acridine has a strong carcinogenic potency on mouse skin, but a very faint effect as measured with the sebaceous gland suppression test4. A sample of this compound was obtained from Dr. F. G. Bock4, and the tetrazolium test performed. The result was 1-310, which, according to the criteria, is characteristic for carcinogenicity. Table 1, TETRAZOUUM BLIND TEST OF DIFFERENT TRI^OQUINAZOLINES (TCQ)Compound labelled 12 Test Test prediction Compound Skin carcinogenic result potency0-874 non-carcinogenic 2-methyl-TCQ non-carcinogenic 1-387 carcinogenic TCQ carcinogenic (3 + )3 1-303 carcinogenic 3-methyl-TCQ carcinogenic (2 + )Skin carcinogenic activity refers to the measurements by Baldwin et al, (ref. 6). The carcinogenic potency for mouse skin of tricyclo-quinazoline was demonstrated in 19595. Further research6 showed that different derivatives of this compound revealed very different results, varying from strong carcinogenic potency to non-carcinogenicity. Three substances of this type were sent me by Dr. K. W. Baldwin6. The substances were labelled 1, 2 and 3 respectively, and were unknown to me until all the experiments were finished. Table 1 demonstrates the results. There is a complete correlation between the carcinogenicity of the compounds and the test results.The possible specificity of the tetrazolium test is thus given a strong further support.