Part I of this study [Spratt JS, Meyer JS, Spratt JA: J Surg Oncol 60:137-146, 1995] reviewed the early reports of investigators, predominantly mathematical biologists and statisticians considering the mathematical laws that would describe the growth of a neoplasm. Included were cytokinetic measurements of the mitotic index, thymidine labeling index, bromodeoxy-uridine labeling index, and the relation of these indices to the potential tumor volume doubling time. The actual doubling time of benign and malignant colonic neoplasms were reported. This second part provides the cumulative observations on the actual doubling times of pulmonary metastases, primary pulmonary cancers, skeletal sarcomas, melanomas, a chemodectoma, tumors of maxillary antrum, testicular cancers, prostate cancer, and the relation between the accumulation of multiple primary cancers and growth rates. The most complete data set is for breast cancer concluding that the cancer growth curve is a decelerating curve with great natural variance. Understanding of the rates of growth of human cancers is essential for understanding the spectrum of cancer behavior observed clinically.