A total of 156 raw oyster samples were collected from 23 retail points in Korea between February 13 and April 7, 2006 and were analyzed by a semi-nested reverse transcription-PCR for naturally occurring noroviruses (NoV). As a whole, noroviral RNA was detected in 14.1% (22/156) of the samples, of which 12.2% (19/156) belonged to genogroup I (GI) and 1.9% (3/156) genogroup II (GII), respectively. The frequencies of NoV contamination apparently differed depending on the retail points or harvesting areas considered: however, the differences were not statistically significant.