An outbreak of ovine footrot in Norway in 2008, the first reported since 1948, prompted action to investigate Norwegian isolates of Dichelobacter nodosus. Isolates from sheep, cattle and goats from approximately 100 farms located in 8 of the 19 Norwegian counties were characterized. The potential virulence of the isolates was assessed by the gelatinase gel test (GG-test) to test the heat stability of bacterial proteases1. Isolates that produced heat stable- and heat labile proteases, were categorized as virulent and benign, respectively. All isolates were allocated to serogroup by a multiplex PCR that differentiates fimA variants 2. A subset was serogrouped by slide agglutination and genotyped by Pulsed-field gel electrophoresis (PFGE). Isolates defined as virulent by the GG-test were all from sheep from one county in the south west of Norway. In cases where extensive under-running of the sole of the hoof had been observed in sheep, isolates from the flock were invariably virulent. More than 97% of the virulent isolates belonged to serogroup A. By PFGE, the virulent isolates were genetically similar while a greater genetic diversity was observed among benign isolates. On the grounds that virulent isolates were found in one county only, and that the majority belonged to the same serogroup, and were similar by PFGE it is believed that a virulent D. nodosus strain was introduced to the country recently and has spread locally within one county.