Summary(1) Intraprostatic deposits of 20-methylcholanthrene crystals induced three types of prostatic neoplasms in the ventral lobes of the Wistar rat's prostate gland: adenocarcinoma (2%), leiomyosarcomas (3%) and squamous cell carcinomas (30.3%). The squamous cell carcinomas and adenocarcinomas metastasized. (2) A detailed account of the distribution of invasion and/or metastases of these prostatic tumors to various organs are presented as well as an account on the growth characteristics of transplantable squamous cell carcinomas.