The microbiology of raw milk, traditionally-made Caciocavallo cheese from Molise was studied throughout ripening. Three different media (MRS agar, MRS agar at pH 5.4 and LBS) and four different incubation temperatures (15, 22, 28 and 45degreesC) were used for lactobacilli, and M17 agar and Slanetz & Bartley medium were used for cocci with the aim of obtaining a complete view of the evolution of these microbial groups. The overall microbiological quality of the product was quite satisfactory; enterobacteria were already absent at 36 h following shaping. High counts of lactic acid bacteria were found in the cheese through the 3 months of ripening. The microbial population present from day 1 of ripening consisted essentially of mesophilic lactic acid bacteria, predominantly lactobacilli, which gradually obtained the advantage over the thermophilic strains. The predominant species were as follows: Lactobacillus paracasei subsp. paracasei, Lb. pentosus, Lb. coryneformis subsp. torquens, Lb. plantarum and Lb. brevis together with Lb. casei, Lb. mali, Lb. rhamnosus, Lb. sakei and Lb. coryneformis subsp. coryneformis. The thermophilic lactic acid bacteria could be ascribed to Lactobacillus helveticus, Lb. delbrueckii subsp. bulgaricus, Lb. delbrueckii subsp. lactis and Lb. delbrueckii subsp. delbrueckii. Lactococci were either Lc. lactis subsp. lactis or Lc. plantarum and enterococci were E. faecalis or E. faecium.