Paratuberculosis and to a lesser extent avian tuberculosis, are emerging as potentially serious problems on deer farms in New Zealand. To date, the majority of reported cases have been subclinically affected animals detected at slaughter, usually with mesenteric lymph nodes lesions which are a nuisance value to the venison industry and financial loss to the farmers due to their gross and histological similarity to lesions caused by Mycobacterium bovis. Recently however, there have been a number of outbreaks of severe clinical disease in 8 to 15 month old red deer. Serological tests are useful in clinically affected animals although they cannot differentiate between M. paratuberculosis and M avium. Studies were undertaken to compare the sensitivity of the agar gel diffusion test, various ELISA tests, the complement fixation test, the lymphocyte transformation test, the comparative skin test and faecal culture for the detection of subclinically infected hinds in a herd of red deer which had experienced a severe outbreak of clinical paratuberculosis in yearling animals. The results will be presented at the conference.