HER2/neu and TGF-beta1 are over-expressed in various types of malignancies. It appears that they play an important role in the biologic behavior of tumors and have prognostic value. Gestational tropoblastic diseases (GTDs) comprise of a heterogeneous group characterized by abnormally proliferating trophoblastic tissues, ranging from benign to malignant. The objective of this study was to measure and compare the serum levels of s-HER2 and TGF-beta between patients with GTDs and pregnant and non-pregnant controls. Serum levels of s-HER2 and TGF-beta1 were determined by ELISA method in 95 GTD patients (55 complete moles, 32 persistent moles, and 8 choriocarcinoma), 30 normal pregnant controls, and 22 normal non-pregnant controls. Mean serum level of s-HER2 did not differ significantly between patients and controls. TGF-beta1 serum level was significantly higher in GTD patients (20.29 +/- 10.68 pg/ml with 95% confidence interval (CI) of 18.10-22.48 pg/ml) compared with pregnant controls (10.26 +/- 11.84 pg/ml with 95% CI of 5.75-14.76 pg/ml) and non-pregnant controls (7.27 +/- 9.61 pg/ml with 95% CI of 3.01-11.53 pg/ml) (P < 0.001). Our findings suggest that TGF-beta1 serum levels in GTD patients may represent a potential prognostic marker. Further investigations with larger sample size and more frequent sampling are required to elucidate this issue.