In the northern regions of Norway, 123 cases of Campylobacter jejuni gastroenteritis were either sporadic infections or due to five separate outbreaks during 1980-83. Using a serotyping scheme based on thermostable antigens and the passive haemagglutination technique, 92 isolates were serotyped. Excluding duplicates from the outbreaks, the serotype distribution based on 79 isolates showed that serotypes 6, 7 and 12, 40 were the most frequent in occurrence. Each included 11 (13.9%) of the isolates and each serotype was also identified twice as the epidemic strain in four different outbreaks. A fifth outbreak strain was serotype 13, 16, 50. The number of isolates that reacted in one or more antisera of the cross reacting group of serotypes 4, 13, 16, 43 and 50 was 21 (26.6%). The other 23 isolates fell into 19 other serotypes and 13 (16.5%) were untypable.