Raw milk and dairy products contaminated with pathogens such as Salmonella spp., Escherichia coli O157: H7 and Listeria monocytogenes may be involved in outbreaks of foodborne diseases (FBD). In the present study we investigated the presence of these microorganisms in artificially contaminated bovine milk, using conventional microbiological techniques and simultaneously by a multiplex PCR. The molecular technique was standardized as pre-enrichment broth SEL (Salmonella, E. coli O157: H7 and Listeria), the sensibility was 10UFC/ml for Salmonella and L. monocytogenes and 1UFC/ml for E. coli O157: H7, and specificity was evaluated with microorganisms from nine different genera. Using both methods were evaluated 600 samples of raw milk, from an equal number of farms of dual-purpose cattle production. The sampling was performed for convenience in three dairy microregions: sabanas of Cordoba and Sucre, Valles of Cesar and Alto Magdalena-Magdalena Medio, the distribution of the samples was proportional, approximately 200 samples per region. For L monocytogenes prevalence was 0.3% (2/600) for Salmonella spp. in 0.8% (5/600) and E. coli O157: H7 in 3.7% of the samples analyzed (22/600). The multiplex PCR for detection of E. coli O157: H7 was more sensitive than conventional method, for Salmonella detection time was reduced to ten hours. The prevalence of E. coli O157: H7 was found associated with the geographic region was statistically significant. The presence of this organism in raw milk can be considered a human health risk