Tie-stalls used to be the common type of housing system for dairy cows in the Parmigiano-Reggiano cheese area; however, the proportion of free-stall herds has greatly increased over the last years. The aim of this study was to compare the milk characteristics between bulk tank milk produced in free-stall and tie-stall herds, in the Parmigiano-Reggiano cheese production area. Fourteen free stalls and 14 tie stalls were involved in the study. Bulk tank milk samples were collected monthly from each herd over a 3-year period. The following parameters were determined for each sample: fat, crude protein, titratable acidity, total bacterial count (TBC), somatic cells (SCC), coliforms, clostridial spores and rennet coagulation properties. Milk produced by free-stall herds (F-milk) showed higher fat, protein and SCC values (3.82 vs 3.61 g. 100 g−1; 3.45 vs 3.30 g. 100 g−1; 158,891 vs 426,088 cells.mL-1, respectively) than milk collected from tie-stall herds (T-milk). The percentage of samples with optimal coagulation profiles and exceeding 100 clostridial spores.L−1 were higher in F-milk than T-milk. F-milk proved to be more suitable for manufacturing Parmigiano-Reggiano cheese both, in terms of yield and quality, although the presence of clostridial spores should be considered, as these microorganisms are responsible for most Parmigiano-Reggiano cheese defects. Yearly and seasonal variations of milk characteristics were also analysed. During the summer, an increase in the TBC, SCC and coliforms were observed regardless of the housing system. In conclusion, besides the type of housing system, it is advisable to adopt management strategies which will reduce the negative effects on milk quality caused by the adverse climatic conditions which occur in summer in the Po Valley.