The factors influencing the growth and metastatic behavior of experimental animal tumors are examined. 10(4) TA3Ha cells were injected intraperitoneally, intravenously, subcutaneously into the flank, and subcutaneously into the tail tissues of syngeneic strain A mice. The tumor takes from these injections were 50/50 (100%), 1/10 (10%), 10/10 (100%), and 7/12 (60%), respectively. The frequency of lung metastasis from these sites was 0, 100, 50, and 100%, respectively. At the time of host death, the flank and tail tumors were, respectively, 2.2 +/- 0.5 cm (geometric mean diameter) and 1.2 +/- 0.3 cm in the TA3Ha and 0.9 +/- 0.1 cm and 0.4 +/- 0.1 cm in the L1210 systems. TA3Ha tumors metastasized regularly to the lymph nodes but the L1210 tumors seldom metastasized to the lymph nodes. Tail implants of TA3Ha tumors behaved similarly in the athymic nude mice and strain A mice. TA3Ha cells inoculated into the Millipore chambers and maintained in mice for greater than 150 days were viable and able to form tumors. The results demonstrate that the anatomic location of the tumor affects the growth and metastatic behavior of the tumors, and that the tumors of different histologic origin metastasize differently even when grown in corresponding locations.