Since viral infections are believed to be one of the causes of sudden hearing loss we have used serological assays for herpes simplex virus (HSV), varicella zoster virus (VZV), and enterovirus as well as polymerase chain reaction for enterovirus to test 55 sudden hearing loss patients for viral infections. Serological screening of these patients for HSV and VZV failed to reveal significant differences between the patient group and the controls. In contrast, enterovirus sequences were detected by RT-PCR in 40% of the patient group, but in none of the controls, suggesting that enterovirus infections may be associated with sudden hearing loss. J. Med. Virol. 72:625–629, 2004. © 2004 Wiley-Liss, Inc.