The microbiological controls (determination of the total and mycetic bacterial count; isolation of enterococci, Clostridium, Pseudomonas aeruginosa, Staph. aureus, E. coli, Salmonella and other Enterobacteriaceae) executed on 1517 samples of 100 varous raw materials, have ascertained the presence of a microbial contamination varying to matters, with presence also of pathogenic or hygienically undesirable microrganisms. The more contaminated substances have resulted to be those organic either of vegetable or animal origin. Sensible differences have been noted between the various lots and according to the various suppliers. The conservation trials under various conditions of temperature (15-22-37 degrees C) and humidity (30 degrees - 60 degrees - 90 degrees of relative humidity) with opened or closed recipients, have demonstrated the possibility of remarkable increases of the number of the microrganisms in the raw materials with increase of temperature and humitidy, especially in the non hermatically closed recipients.