Thirty-two cases of hydatidiform mole without endometrial invasion of chorial tissue and 17 of invasive mole were studied to ascertain whether these two diseases can be differentiated by various immune parameters. All of hydatidiform 11 of invasive mole were sampled at a state of "mole in utero" (pre-evacuation), but 6 of invasive mole were at a post-evacuation state, respectively. The results were summarized in the following items; 1. Serum total protein, especially albumin decreased with no significant difference in both groups. Globulin fractionation (alpha 1, alpha 2, beta, gamma-globulin) showed no characteristic changes. 2. A variation of immunoglobin (IgG, IgM, IgA) was similar in both. 3. Beta 1 C (a component of complement) increased in two groups, but no difference was revealed. 4. Leucocytosis was observed, but lymphocytosis was not detected in both groups. 5. Active E-RFC slightly increased, although total E-RFC and EAC-RFC were within normal range. But these findings were not statistically different in both. 6. In vitro lymphocyte-PHA-response was fairly depressed without a significant difference in two groups. 7. Suppressive effect of serum on lymphocyte-response was also slightly strengthened, but a difference in both was not significant. 8. The results of immune skin tests (PHA, PPD, SK-SD, Candida) could not be debated with liquid numbers studied.