Results gained in a placebo-controlled, clinical double-blind study with the Herpes antigens LUPIDON H and Lupidon G are reported. Due to treatment with LUPIDON H or LUPIDON G a cure or a more soothed course of the disease and among the indicated effects a prolongation in length of the intervals during which no relapses occurred could be observed with regard to about 80% of all the patients concerned. In opposition to the mentioned effectiveness the treatment success becoming evident after the administration of Placebo under equal test conditions was only evaluated with a rate complying to approximately 30%. The difference determined at those investigations with reference to the efficacy of LUPIDON (80%) in comparison with Placebo (30%) is statistically significant. This outcome confirms the results already observed hitherto in open clinical investigations by other examiners whose findings, too, ascribed to LUPIDON a favourable influence on Herpes simplex diseases in about 80% of treatment cases.