To control the epizootic of avian tuberculosis within the collections of captive wildfowl of The Wildfowl and Wetlands Trust an efficacious vaccine and a reliable diagnostic test are required. A number of potential diagnostic tests were compared for sensitivity and specificity using a flock of 178 feral barnacle geese (Branta leucopsis) at The Wildfowl and Wetland Trust's centre at Slimbridge, Gloucestershire. Evaluations were made of: serodiagnosis by an enzyme-linked immunosorbent assay (ELISA); agglutination of a suspension of killed Mycobacterium avium using both whole blood and serum; and haematological analysis. Necropsy findings confirmed the ELISA to be sensitive and specific, and capable of detecting the disease even at an early stage. The agglutination tests were quick and easy to perform although a number of false positives and negatives did occur. The haematological analysis was found to be less sensitive. ELISA and agglutination tests are now being used to screen the birds in the collections.