An analysis of the Stanton et al. (1981, J. Natl. Cancer Inst. 67, 965-975) data reconfirms number of index particles as the primary dimensional predictor of tumor incidence. Fitting separate intercepts and/or slopes to each mineral type results in substantial significant improvement in fit, indicating the importance of mineral type. This contrasts with the "Stanton hypothesis," which states that dimensional properties alone determine carcinogenesis. Log mean aspect ratio is not as good a predictor of tumor incidence as the number of index particles; among those samples that did not have index particles, log mean aspect ratio is not a significant predictor of tumor incidence.