Variations in the hygienic quality of raw milk collected at different levels of the dairy chain from the farm, tanks, at the end of collection and at delivery in the north-central region of Algeria were studied over a period of one year. The average loads of all the germs of contamination increased gradually (p<0.001). The average values of these respective evolutions of the farm, at the end of collection and delivery, expressed in Log10 cfu/ml of raw milk for total aerobic mesophilic flora (TAMF), total and faecal coliforms (TC), (FC) values are (5.11, 6.42 and 7.5), (3.1, 4.6 and 5.31), (1.61, 3.29 and 4.29). Yeasts and molds are present with high levels of contamination in the samples analyzed, the average per milliliter expressed in Log10 cfu at each collection site are respectively (2.84, 4.58 and 5.34), (1 24, 3.23 and 3.88). The pathogenic flora also has increasing presence rates at each level of the dairy chain. Milks from farms that were already contaminated with Clostridium, Listeria monocytogenes, and Staphylococcus aureus (15.27, 1.39 and 4.86%), respectively, arrived at the different dairies with exponential mean presence (50; 28.33 and 56.66%). However, it should be noted that the danger is all the more important as the presence rate and the microbial load are higher in raw milks. The strong growth of the micro-organisms studied once again demonstrates the variability of practices from one sampling site to another. This is the result of poor hygienic conditions during milking, they also provide information on the degree of handling of milk, including the observed transvasions.