A herd of 350 beef cows aged 2 years and over, have about 3-4 animal deaths per year showing typical diarrhea signs of paratuberculosis. The herd was followed from 1992 to 1995 with simple comparative skin testing, avium PPD and mammalian PPD (SENASA - Argentina). Tests were performed in the neck and the reaction was read 72 hrs post inoculation. Skin fold differences over 3 mm were regarded as positive, with 17% positive reactors. From the herd, 145 animals were chosen at random in 1995 for EIA-IFN-gamma and absorbed ELISA (CSL, Australia) tests were performed according to manufacturer's instructions. Rendering 2% IFN-gamma positive (3 animals), an avium culture OD that was 0.100 above the control culture's OD value was regarding as positive. Responsiveness to M. avium PPD was indicated by calculating the ratio less than 0.7 of ELISA OD values for the bovis PPD culture to the avium PPD culture. With the absorbed ELISA, 2.75% of the animals were positive (4 animals) with the positive cutoff value being the negative control plus 0.100. Two cows were IFNgamma , ELISA and skin test positive (skin test was performed 6 months prior to blood sample extraction). Due to contamination, cultures were not available from all animals, but we have recently isolated M. paratuberculosis from a symptomatic cow. We have compared these sera with another ELISA-absorbed indirect system using absorbent from M. phlei according to Cok et al method. Sera dilution was 1/20, antigen used was M. paratuberculosis PPD (Allied Monitor), conjugate IgG (Denmark) and ABTS as chromogen. Main cross reaction prolem which in Argentina is due to related mycobacteria like M. bovis, encouraged us to use sera from a cow with reaction to mammalian PPD as cutoff, prior to absorption with M. phlei soluble antigen for 30 minutes, sera incubation and conjugation for 1 hour. In this ELISA system, 3.4% of animals were positive (5 animals). We also tried to use avium PPD (SENASA-Argentina) as ELISA antigen, but no sera reaction was observed.