Thirty-five patients affected by acute vestibular dysfunction (A.V.D.) and/or sudden deafness (S.D.) were studied. Twenty-seven of them presented, as major component of the clinical disorder, a vestibular dysfunction, eight a sudden deafness. The control group was matched for sex, age, smoking habit and family history of diabetes and myocardial infarction. In all the subjects the following tests were carried out: platelet aggregation (Born's method), PF3 (Spaet and Cintron), PF4 and BTg (RIA), aPTT, AT III, cholesterol and triglycerides. The results indicate in the patients group increase of P.A.: SAV = 27 vs 43% (p = 0.03) at 1.2 X 10(-6) M ADP, a larger availability of PF3 in PPP and PRP, increase of PF4: 7.2 vs 17.2 (p = 0.01) and BTg: 32.4 vs 49.1 (p = 0.009). The data indicate in A.V.D. and S.D. a platelet hyperactivity; if so, an antiplatelet therapy may be reasonable.