The problem of invasive pests and diseases has become more urgent and far more complex today than in the recent past. Increased trade and movement of people, and the opening up of new trade routes have increased opportunities for the spread of invasive species. In addition, mono-cropping systems of cultivation; globalization; increased resistance of pests to pesticides and food safety and environmental concerns have all contributed to the growing complexity of the problem on hand. The economic dimensions of the problem can be viewed from at least two perspectives. First, with regard to the spread and impact of invasive species, particularly how best to provide more comprehensive assessments of impacts of invasions, so as to improve the cost effectiveness and efficiency of publicly funded programs aimed at eradication, control or mitigation of invasive pests and diseases. Second, from the perspective of incorporating more economic analysis and use of economic instruments in designing sanitary and phytosanitary measures. The paper explores some of these issues from an economic perspective. It concludes that incorporating more economic analysis in matters related to biological invasions is desirable, but presents a challenge to economists. Measurement requires data, and success in measurement will require that economists and biological scientists work closer together than they have in the past.