The cytotoxicity of four tumorigenic minerals, erionite(w), erionite(c), UICC crocidolite, UICC chrysotile to Chinese hamster V79 cells was compared. The results indicate that the minerals were toxic by showing more than 50% toxicity for at least one dose between 10 and 100 micrograms. This confirms the previous findings that V79 cytotoxicity corresponds to the tumorigenic potentials of the mineral fibers. Higher potency of erionite, however, was not evident in the system when the dose considered was expressed in mass units. On the other hand, when the degree of cytotoxicity was considered per number of mineral fibers, it was clear that fewer erionite fibers of all three dimensions (A greater than or equal to 3; L greater than or equal to 8.0 micrometers, W less than or equal to 0.25 micrometers; and L less than or equal to 5.0 micrometers, W less than or equal to 0.1 micrometers) than those of UICC crocidolite and UICC chrysotile were needed to produce similar toxicity. This suggests that the dose in number of fibers may be a better parameter than the total mass dose as a correlate of tumorigenic potential. (Copyright (c) 1988 by Academic Press, Inc.)