Sixty-one patients suffering from primary varicosity were divided into 2 groups, one receiving regular hydrotherapy, the other no such treatment for 31/2 weeks. Objective evaluation of the venous competence showed an apparently greater benefit in the control group in respect to light reflex rheographic venous filling time. The leg volume changes, however, indicated a stronger and more persistent reduction in the experimental group. The same applied for ankle and calf circumferences, which were reduced significantly only in patients treated with hydrotherapy. Furthermore some (but not all) of the subjective symptoms yielded significantly more frequent improvement in this group. In conclusion this controlled study implies that hydrotherapy may help patients suffering from primary varicose veins, a notion which was previously often stated but so far not scientifically verified.