Outlines a simple linear cost-benefit model for determining whether it is economic at the farm-level to vaccinate or dose a batch of livestock against a disease. This model assumes that total benefits and costs are proportional to the number of animals vaccinated. This model is then modified to allow for the possibility of programmes of vaccination or disease prevention involving start-up costs which increase, but at a decreasing rate with batch size or with the size of the herd to be vaccinated. In this case, vaccination is more likely to be profitable the larger is the herd or the batch size. Consequences of uncertainty for economic decisions about vaccination are considered. The minimax gain criterion, minimax regret criterion and expected gain criterion are applied to vaccination choices under uncertainty. Other things equal, risk-aversion or uncertainty avoidance increases the likelihood of farmers vaccinating their animals. Attention is brought to the need for research on the economics of improving estimates of the likely occurrence of livestock diseases.