Three chronically paratuberculosis infected herds were tested for six years twice a year (intradermal Johnin test, antibody ELISA (IDEXX Corp.), microbial culture) according to a sanitary program. Culling of shedding animals and vaccination of calves with NEOPARASEC (Merial Corp.) were part of the program. In course of experiment, 1015 samples of 228 non vaccinated cows and 1502 samples of 293 vaccinated cattle have been tested. 3.8% of the vaccinated animals proved positive in microbial culture. Nearly all vaccinated calves developed granulomas sized from hazelnut to loaf at the injection site. Positive reactions in intradermal test as well as in antibody ELISA were found in very young calves. 24.3%, 33.7%, 25.9%, respectively of the non vaccinated animals were identified as shedders of M. avium subsp. paratuberculosis (MAP) by microbial culture. In the first and in the second herd most shedders of MAP were found in the first herd examination (66.7%, 42.9%, respectively), whereas in the third herd they were detected in the fifth examination (31.0%). At the beginning, 17.9% of non vaccinated animals proved positive in intradermal test, 14.4% in antibody ELISA. Afterwards, the number of positive test results decreased but increased again towards the end of the experiment. 48.5% of the 66 shedders showed positive reactions in intradermal test, 57.6% in antibody ELISA, 77.3% in at least one of these both tests. Antibodies in ELISA were found in rising frequency from two years before the time of shedding. 50.0% of the shedders reacted positive in ELISA at the time of shedding. In selected shedders first positive results were found at the age of about two years. Unfortunately, only incomplete hygienic measures were realized by the farmers. Under field conditions the realisation of attending sanitary programs is difficult. MAP is spread mainly by buying of animals, therefore a certification program for paratuberculosis free herds is urgently necessary as well as an improvement of diagnostic methods.