Studies of human prostate carcinoma (PCA) have been hampered by only a few cell systems from already-metastatic human disease. We have developed a novel cell system by using tissue cultured CWR22R cells from a xenograft of a primary tumor from a human patient. These cells were transfected with the bacterial lacZ gene to maximize their detection during progression and metastasis in nude mice. LZ-CWR22R cells are extremely stable for lacZ expression over 25 passages and metastasize to lung, liver, and bone from the subcutis - major sites of metastasis of the human disease. A matrigel vehicle facilitated development of primary tumors and micrometastases in all organs. While some micrometastases developed into overt metastases, others remained as micrometastases for long periods of time, possibly providing a model of latency of metastatic disease. An experimental metastasis model (tail vein injection) also generated micrometastases in lung, liver, and bone with differing kinetics of formation and stability. Serial sections of many individual lung micrometastases within one hour of injection indicated considerable heterogeneity in cellular composition (from 1 to 19 cells/site) while liver sites at later times were comprised of only 1 or 2 cells (the size of bone sites were comparable to those of liver). By combining use of these histochemically-tagged PCA cell systems with high resolution molecular analyses (laser-capture microdissection), it will now be possible to analyze gene expression patterns characteristic of micrometastases developing in several different organs.