The proportion of mastitis infections in dairy cattle caused by environmental pathogens has increased in recent years. The number of microorganisms in bedding materials affects the incidence of udder infections. The objective of this study was to describe a diagnostic method suitable for the evaluation of environmental mastitis risk due to microbiological bedding material quality, and how this method can be interpreted or constructed. Material and methods: A sample of 1 g of fresh bedding material (straw: n = 406; wood shavings: n = 281) was mixed with water in order to create a homogenized blend of bedding material that was used for a dilution series according to German law standard (§64 LFGB, method: L00.00 54). Subsequently, the total aerobic bacterial count as well as the bacterial counts of Escherichia coli, coliform bacteria and aesculin-positive streptococci were determined using pour or spread plate techniques (§64 LFGB L01.00-57) on different (selective) agar media. The determination and calculation of bacterial counts were carried out after a defined incubation time. Results: In common bedding materials, there is a huge variability of the bacterial count. While hygienically perfect bedding materials regularly show total aerobic bacterial counts of < 10 ⁶ barely exhibit any coliforms or aesculin-positive streptococci, bacterial count thresholds can be exceeded in optically perfect fresh organic bedding materials even before first use. These materials are therefore regarded as high risk. Conclusion and clinical relevance: The microbiological investigation of fresh bedding materials provided evidence for the evaluation of environmental mastitis risk. Naturally, the contamination of the bedding areas with faeces, urine and milk, along with frequency of changing the material, care requirements and barn climate are also important considerations to take into account for the reduction of the bacterial counts in the bedding area.