-Raw cow milk microflora: diversity and influence of conditions of production . The microbial composition of 158 raw cow milk samples taken from 27 farms located in the French Alps area was determined. Microbial analyses included the total mesophilic aerobic bacteria count as well as numeration of some useful cheesemaking microorganisms (lactic acid bacteria, halophilic bacteria, propionic acid bacteria…), spoilage bacteria (Pseudomonas, enterobacteriaceae, Clostridium spp.) and some of the pathogenic bacteria (coagulase positive staphylococci, Escherichia coli). Milk samples were of good overall microbial quality (mean value less than 10 000 cfu . mL -1 ) and had different contents of useful cheesemaking microorganisms or spoilage bacteria. Five different groups of milks were then separated according to their total count and to their relative contents in useful cheesemaking and spoilage microorganisms. When incubated at 37 o C for 24 h without any starters addition, milks of the different groups did not have the same ability to produce acid and to coagulate. At the farm level, milk suppliers practices were studied. Farmers differed by their way of washing the milking equipment and by their pre-milking and post-milking udder preparation. Combination of these practices influenced the microbial load and composition of the milk produced. microbial composition / raw milk / farmer practice Résumé -La composition microbiologique de 158 échantillons de laits crus de vache prélevés à la fin de la traite chez 27 producteurs des départements de Savoie et Haute-Savoie a été étudiée. Seize groupes microbiens ont été choisis parmi les groupes d'intérêt technologique (flore acidifiante méso-phile, flore halotolérante, bactéries propioniques…), les groupes d'altération (Pseudomonas, entéro-bactéries, Clostridium spp.) ou certains groupes potentiellement pathogènes (staphylocoques à coagulase positive, Escherichia coli). Si en moyenne les laits analysés renferment très peu de germes (moyenne inférieure à 10 000 ufc . mL -1 ), il est possible de distinguer 5 classes de laits qui diffèrent par leur teneur en flore mésophile aérobie revivifiable (de 1 200 à 15 000 ufc . mL -1 en moyenne) et par leur proportion en flore d'intérêt technologique et en flore d'altération. Les laits des différentes 575 * Correspondance et tirés-à-part Tél.