A PCR test based on IS900 oligonucleotide sequence has been developed to detect Mycobacterium avium subsp. paratuberculosis in bovine feces. An internal control has been developed for each PCR test to avoid false negative results often obtained with inhibitors contained in feces. The detection threshold of this test was determined by dilution of a suspension of M. avium subsp. paratuberculosis in bovine feces. The level of detection has been evaluated approximately to 50 CFU/g of feces. The specificity of the test has been assessed on 45 strains of M. avium subsp. paratuberculosis and 48 other mycobacteria (representing 13 species), 42 other bacteria (20 species) and 27 bovine feces fungi. None of bacteria, fungi and others mycobacteria tested gave a postitive signal. All the 45 M avium subsp. paratuberculosis strains gave a positive result. For field evaluation, between June 1999 and July 2000, 1041 bovine feces were collected from French herds suspected to be infected by M. avium subsp. paratuberculosis and were analyzed by culture or by PCR. Infected animals were found in 15 herds by culture and 17 herds were PCR positive. 72 feces samples were found positive by culture and 77 feces samples were found positive by PCR. Both methods show an equivalent sensitivity in term of herds but some discrepancy on individual results has been observed. These different results between the 2 methods could be due to the heterogeneity of the feces. This heterogeneity could give discrepant results, especially for low contaminated samples.