The economic costs of cystic echinococcosis (CE) in Wales, which is part of one of the most highly developed, industrialized countries in the World, were evaluated. In this region, the disease in both sheep and humans causes financial losses. The sheep-related costs in the most highly endemic area, of southern and mid Wales, were estimated from recently published prevalences of the disease in local sheep. No relevant and recent data were available on the sheep in the rest of Wales but these animals were assumed to have lower prevalences, in line with historical data, and were ignored in the economic analysis. The costs of the disease in humans were based on published incidences of human cases treated surgically and the costs of surgery as estimated from hospital records and by costing out the procedures each patient received whilst undergoing treatment. The quality of life of patients treated for CE was also determined and compared with that of healthy, case-matched controls, using a standard health-survey questionnaire (SF-36). The results indicated that the treated patients suffered some long-term morbidity, caused by the disease itself, its treatment or both. Although accurate monetary values were not calculated for this decreased quality of life, the results indicate that the economic effects of human CE are greater than simply the cost of treatment. Assuming that the long-term morbidity demonstrated does have an economic effect, each year CE in Wales is probably costing the U.K. economy more than U.S.$1 million, and perhaps as much as U.S.$7.9 million.