A methodology is described to establish the relative financial benefit of farm animal disease prevention (biosecurity). This methodology is demonstrated using the example of bovine viral diarrhoea virus (BVDV) incursion on beef suckler farms in Scotland. A random sample of 276 herds was taken and a proportion of young stock on each farm tested for previous exposure to BVDV. There was evidence that 0.4 of herds had been exposed over one year prior to sampling. All herds completed a questionnaire about their biosecurity practices. The influence of these practices on relative risk of BVDV was subjected to a Chi squared test and practices ranked accordingly. Most important risk factors were animal buying in strategy, farm size and a single farm boundary. The economic benefit/disbenefit of these strategies was assessed using a bio-economic model of a 10-year BVDV epidemic. Expected output losses due to BVDV infection and risk were affected by biosecurity strategy and by level of biosecurity threat. The implications of these findings for animal health strategy at farm and regional level are discussed.