Idiopathic sudden hearing loss (ISHL) has been suggested to precipitate as final common pathway of microcirculatory impairment of the inner ear associated with a variety of etiologies and characterized by a local hyperviscosity syndrome in cochlear vessels. Therefore, we investigated the effect of Rheopheresis, a method of therapeutic apheresis reducing plasma viscosity and improving microcirculation on hearing recovery. Patients were randomly assigned to receive two Rheopheresis treatments, or treatment according to current German guidelines consisting either of i.v. corticosteroids (methylprednisolon 250 mg for 3 days and subsequent oral dosing with tapering to zero) or i.v. hemodilution (500 mL 6% hydroxyethyl starch plus 600 mg pentoxifylline per day), each applied for 10 days. The primary outcome parameter was absolute recovery of hearing as measured by pure tone audiometry 10 days after the start of treatment. Secondary outcomes were recovery of hearing at day 42, the improvement of speech audiometry, tinnitus and feeling of pressure and the frequency of adverse events. In total, 240 patients with sudden hearing loss were enrolled from otorhinolaryngological departments at hospitals as well as out-patient clinics in Germany. Analysis was performed for the intention-to-treat as well as per protocol population. Mean absolute recovery of hearing on day 10 within the intention-to-treat population (ITT, n = 193) was 23.95 dB (SD 15.05) in the Rheopheresis group and 24.29 dB (SD 15.48) in the control group. Equal efficacy of Rheopheresis and tested standard treatments was demonstrated (P = 0.00056). Single Rheopheresis led to a higher recovery of hearing after 48 h in patients with high plasma viscosity (>1.8 mPas s; P = 0.029) or high total protein (>74 g/dL; P = 0.02). However, an overall good recovery of ISHL was observed with none of the tested therapies being superior regarding the primary outcome parameter. Improvement of health-related quality of life as documented by the SF36 was higher in the Rheopheresis group, exhibiting a significant difference for the physical summary scale at the final follow-up at day 42 (P = 0.006). In conclusion, Rheopheresis proved to be an effective treatment option within the ENT armamentarium for ISHL. Two Rheopheresis treatments within 3 days lasting for about 2 h each could be used to replace a 10-day infusion regimen, especially in patients who desire fast recovery from acute hearing loss. Also, this may be a second line treatment option for patients refractory to i.v. corticosteroids or hemodilution.