Biosecurity is the set of practical measures introduced in a production system in order to prevent and/or control the entry, dissemination and exit of harmful biological agents. The main objective of this study was to survey the biosecurity practices adopted in milk production systems and relate the existing biosecurity practices to the size of the properties. Qualitative variables were submitted to the chi-square test to verify associations between the frequencies of questionnaire responses and farm size. Multiple Correspondence Analysis (MCA) was performed using the free trial version of JMP software that is part of the SAS program. In general, large farms were more likely to carry out biosafety measures to protect against biological risk when compared to small farms. These include the presence of implemented visitation policies (OR 12.889; 95% CI 2.307-72.016), acquisition of equipment such as tractors or trucks for towing and transporting animals (OR 33.750; 95% CI 3.709 – 307.128) and ease of isolation of sick animals compared to healthy animals (OR 13,175 - 95% CI 1,549 – 112,032). Medium-sized herds were 8 times more likely (95% CI 0.821 – 78,000) to undergo cleaning and disinfection procedures after an episode of on-site abortion when compared to small-sized herds.