This study concerns the relative value of a serological ELISA test compared to the methods of complement fixation test (CFT) and faecal culture habitually used for Paratuberculosis screening. The specificity study of the ELISA technique was conducted on adult animals from herds in the Haute-Vienne recognised as disease-free and having had negative faecal culture results for 5 years (n = 522). It was conducted too by analysis at the Departmental Veterinary Laboratory of the Aveyron of a population of animals less than 24 months old from herds not presenting symptoms but without a known history in terms of faecal culture for Paratuberculosis (n = 1000). The examination of these populations enabled us to observe a specificity for the ELISA technique that was greater than or equal to 99.9. The relative ELISA detectability was evaluated in comparison to CFT by analysis of successive dilutions of strongly positive sera. This study enabled us to ascertain that the evaluated ELISA method was able to provide positive results with antibody concentrations as much as 4 times lower than those yielding positive results with CFT. This observation helps to explain, in particular, the frequency of conflicting CFT negative/ELISA positive results. The relative sensitivity of ELISA and faecal culture was evaluated by analysing, every 90 days for two years, all of the animals in an infected herd (n = 80), of high genetic value, with regular follow-up, evolving in natural conditions. This study enabled us to establish that in two-thirds of the cases, the use of the serological test permitted an earlier diagnosis than with faecal culture. In one third of the cases, the use of the faecal culture technique led to an earlier diagnosis than the ELISA technique. The use of these tests in combination or ELISA alone is debated.