AbstractSpreadsheet models were constructed to assess the economic impact of some 30 non-notifiable diseases of farm animals in Great Britain. A standardized methodology and common valuation base were used to derive estimates of the direct costs to livestock production of each disease, separately identifying the costs associated with disease output losses and those relating to disease treatment and prevention. Disease data limitations and uncertainties are incorporated into the estimation procedure. The spreadsheet models are highly transparent with calculations and the origin of parameter values clearly documented. The assessments of six bovine diseases, are presented: BVD, fasciolosis, lameness, leptospirosis, mastitis, and summer mastitis, and full details of the analyses of all the diseases can he accessed on the internet. The models do not consider the wider economic impacts of disease, such as effects on markets, human health and animal welfare. However, the approach is a simple and transparent one which enables exploration of the direct costs associated with a range of livestock diseases and which is easily communicated to policy makers and others.