It has been suggested that uPA in cancer cells is up regulated by the p 185 kD form of the HER-2/neu oncogene. We elected to see if the extra cellular domain of HER-2/neu, the p 105 fraction, which is found in the circulation, has any regulatory influence on uPA or uPAR in those patients with NSCLC Levels of uPA, uPAR and p 105 HER-2/neu were determined in blood from age-matched controls and patients with advanced NSCLC. In the patients with NSCLC, samples were obtained before and following treatment. A large increase in both uPA and uPAR compared to controls was seen in the patients prior to treatment. The uPAR level post-treatment decreased from pre-treatment values, which is favorable. There was a significant increase in uPA and a decrease in HER-2/neu in the post-treatment time frame. Additionally, correlation analysis of circulating uPAR, uPA and HER-2/neu against each other in both the controls and treatment groups indicated no relationship. It appears that circulating uPA and uPAR are elevated in NSCLC patients. The up-regulation of uPA by HER-2/neu seen in lung cancer cells in vitro is apparently lost in the blood in vivo as is evidenced by the lack of correlation between them which is also true for the receptor as well.