Grazing of cattle and sheep on the same pastures is not uncommon in the Netherlands. Until now these sheep play no role in the control measures proposed for the prevention of paratuberculosis in cattle. A thorough investigation of sheep on farms with a known history of paratuberculosis in cattle was instigated to assess the validity of this approach. Early 1998, 18 farms with both sheep and cattle were selected for further study. Selection was based on a positive paratuberculosis diagnosis in one or more cows during the years 1996-1998. Cattle and sheep on these farms were grazing on the same pastures or the sheep pastures were fertilised using manure of the cattle. All sheep more than one year of age (n = 919) were serologically tested using an absorbed ELISA (Ubitech). The number of sheep per flock varied from 15 to 133. Serum samples with an S/P (Sample to Positive) ratio > 0.3 were regarded as positive. Five flocks had 1 serologically positive sheep, all the other samples tested negative. The 5 positive sheep and 45 others, based on the condition of the animal, most suspected sheep, were purchased from 15 farmers. The number of purchased sheep per flock varied from 2-6. These 50 sheep were necropsied in the period June-September 1998. Extensive examination of jejunum, ileum, ileocaecal valve, ileocaecal, mesenteric and retropharyngeal lymph nodes and intestinal contents, was performed by means of culture, histology and Polymerase Chain Reaction.