A new cell line, PPC-I, has been established from a specimen obtained from a patient with a poorly differentiated adenocarcinoma of the prostate. This is the first line of its type derived from a primary prostatic tumor site. PPC-I cells have become immortalized in culture, exhibit transformation parameters including relaxed growth factor requirements and anchorage-independent growth, and are highly tumorigenic in nude mice. Cytogenetic studies by G-banding revealed a grossly abnormal karyotype, with a modal chromosome number of 84, multiple marker chromosomes including both homogeneously staining regions and double minutes and clonal loss of chromosomes 3, 5, 10, 15 and Y.