It is widely acknowledged that international trade is a major pathway for the spread of invasive species. International agreements and domestic legislation aim to reach a balance between facilitating trade and providing nations with the right to protect their environmental, public and economic health. This is achieved through the development of standards that prescribe procedures that must be followed before a commodity is imported. Under Section 22 of the Biosecurity Act (1993) Biosecurity New Zealand of the Ministry of Agriculture and Forestry (MAF) develops import health standards for the importation of commodities and sea containers and for the approval and management of transitional facilities. Under current regulations, before being allowed to enter New Zealand, a sea container must first be accompanied by appropriate documentation for the sea container itself and any contents (this includes cargo manifests, any required treatment certificates for the cargo and cleaning certificates for the sea container itself). Upon arriving in New Zealand the sea container is transported to a transitional facility for inspection and unloaded once biosecurity clearance has been obtained. There are approximately 7,000 transitional facilities (both on and off wharf) throughout New Zealand and inspections are conducted by persons that have obtained accreditation from MAF for inspections (MAF accredited persons). Based on current importation procedures and other information made available, mathematical models were developed for three sea importation pathways (sea containers, woodpackaging and used vehicles) that involved the inspection of imported units by MAF accredited persons. These models were designed to predict the effectiveness of the current border inspection policies and procedures. Inspection accuracy was found to have the most influential impact on slippage (the rate at which contamination passes through border procedures undetected) along the measured pathways. Under current conditions, an estimated 5.75% of all sea containers, 4.12% of all sea containers containing woodpackaging and 1.63% of all used vehicles that enter New Zealand annually are contaminated in some manner despite having biosecurity clearance. A 3% increase in inspection efficiency reduced slippage to 0.5% of sea containers, 2.16% of woodpackaging and 0.001% of used vehicles entering New Zealand annually. Given that the accuracy of the inspection was the most influential aspect of the border management procedures, mathematical models were develop to predict the cost of compliance recovered by MAF if all inspections were conducted by MAF inspectors as apposed to MAF accredited persons. Under current regulations the cost of compliance (if MAF inspector conducted inspections of all imported units) was estimated to be $117.36 million for sea containers, $35.16 million for woodpackaging and $5.44 million for used vehicles. Increasing the inspection accuracy to the ideal 100% increased the cost of compliance by 75.36%, 61.96% and 61.92% for sea containers, woodpackaging and used vehicles respectively. These findings indicate that Government investment in the training of inspectors throughout New Zealand would improve current border detection rates. Under current regulations, the cost incurred by MAF inspectors inspecting all imported units is recoverable. Currently the cost of compliance is approximately 1% of the value of annual imports. These costs are seen by the import sector as part of their daily business and understand that these measures are in place for the long term sustainability of their businesses (Anon. 2005).