The gene expressions of urokinase-type plasminogen activator (u-PA), u-PA receptor (u-PR), and plasminogen activator inhibitor (PAI)-1 and -2 in human tumor cell lines and human gastric cancer tissues were analyzed using the reverse transcription (RT)-PCR. The expression patterns were compared with experimental metastatic ability in chick embryo or clinicopathological findings. The results indicate that the function of u-PA binding to u-PR and the diminished expression of PAI-2 are significantly involved in the process of cancer metastasis and PAI-2 may be more effective in regulating u-PA activity than PAI-1.