Although the pathogenesis of sudden hearing loss (SHL) is not as yet known, the clinical picture and the frequent association with vascular risk factors make an ischaemic event likely. This study aimed to assess the effect of an extracorporeal procedure (H.E.L.P.) in removing LDL-cholesterol, fibrinogen and lipoprotein (a) from the plasma, on the recovery of hearing SHL. This procedure using the HELP-system was compared with the usual standard treatment with prednisolone, dextranes and pentoxifyllin. We undertook a single centre, prospective, randomized study in which 18 patients were assigned to H.E.L.P.-apheresis and 9 patients were assigned to standard treatment (2:1 randomization). Audiometric and laboratory testing was performed at baseline, 24 h and 6 weeks after start of treatment. Primary endpoint was the improvement of the average pure-tone threshold between 0.125 and 8 kHz after 24 h. Twenty-four hours after H.E.L.P. treatment average pure-tone threshold recovered by 10.4 dB and by 26.4 dB after 6 weeks. The recovery of hearing of the standard treated patients was 5.8 dB and 16.8 dB after 24 h and 6 weeks respectively. LDL-cholesterol, fibrinogen and lipoprotein (a) were significantly reduced in the HELP treated patients compared with standard therapy, resulting in a significant improve in plasma viscosity, erythrocyte aggregation and resistance to oxidative stress of LDL particles. Our results suggest that the clinical outcome of SHL after a single extracorporeal LDL-apheresis is superior or at least equal to the more expensive standard treatment with prednisolone, dextranes and pentoxifyllin. Re-establishment of vascular endothelial function and improved blood rheology may be the underlying cause. These results must be confirmed in larger-scale trials.