A quantitative risk assessment model was developed to estimate the frequency with which meat waste from ships or aircraft might expose British livestock to infection with foot-and-mouth disease (fmd), and investigate the factors that might contribute to the risk. In the model, the total weight of waste introduced that was contaminated with fmd was estimated to be 26 kg per year, with 90 per cent certainty that it would be between 10 and 53 kg. As a result, it was estimated that there would be a mean of 1429 years between outbreaks of fmd due to ship and aircraft waste, with a 90 per cent certainty that the interval would be between 500 and 10,000 years. These estimates were affected by three principal uncertainties: first, the prevalence of fmd; secondly, the probability of the waste being removed and fed to pigs; and thirdly, the probability that overboard dumping of contaminated waste might expose livestock to fmd. The effect of these uncertainties on the model was investigated in a sensitivity analysis.