The aim of this study was to observe the usefulness of betahistine dihydrochloride--Betaserc--in therapy for vestibular disorders in patients with vertebrobasilar insufficiency. Two groups of patients, in each of which were 150 patients (mean age, 52.2 years), were tested on the basis of videonystagmography and stabilometry. Betaserc was administrated in two separate doses: 8 mg three times daily and 16 mg three times daily for 120-180 days (mean, 132 days). In every case before and after therapy, visuo-oculomotor and vestibulo-oculomotor reflexes were tested, and amplitude and velocity of the sway were measured during dynamic posturographic testing. After Betaserc treatment, pathological visuo-oculomotor reactions and pathological cervical test results disappeared in most cases: Smooth pursuit improved in 59.9% of cases and saccadic movements in 55.9% of patients, and cervical nystagmus disappeared in 62.2% of tested people. During stabilometry, mean and maximal platform amplitude and mean head velocity decreased as compared with results from tests performed before treatment. These observations were significant after the greater dose of Betaserc; nonetheless, improvement was noted after both doses. The usefulness of Betaserc in vertebrobasilar insufficiency was proved, 4-6 months' therapy was sufficient, and the effect on central compensation seemed to be most probable.