Noroviruses exhibit a wide genomic and antigenic diversity, making laboratory diagnosis difficult. The abrupt onset of the illness does often not allow timely sample collection. Three different methods (a commercially available ELISA, a published RT-PCR and an RT-booster-PCR) were compared for detecting noroviruses in stools collected after the end of a gastroenteritis outbreak. Both ELISA and the RT-PCR detected noroviruses in 6 samples out of the 41 samples collected and tested. The RT-booster-PCR, however, was able to detect noroviruses in 23 (56%) of the samples with 20 of the samples confirmed by sequencing. Confirmation of PCR products was also undertaken by Southern hybridisation with controversial results (e.g. lack of confirmation on samples positive by sequencing). The results show that common molecular diagnostic methods may fail sometimes to detect the presence of noroviruses in a relevant proportion of samples. A sensitive detection method, such as the RT-booster-PCR described below may resolve the cases.