The capability of Pacific Island countries' agriculture to adapt to climatic and environmental changes is analysed. After presenting key features of the region's food cropping systems, findings of genetic diversity studies for the most important food crops are reviewed and their implications for adaptation are discussed. Biophysical and economic vulnerabilities of the food system are identified. For the major food crops, the needs for genetic improvement are detailed, and practical solutions for broadening genetic bases are suggested. The paper concludes by identifying areas for additional research on crops and agro-ecosystems adaptation aiming at increasing the flexibility of agriculture in the Pacific. In this region, plant breeding has to cope with the insularity constraints of the small island states. The new varieties need to satisfy farmers' agronomic requirements in very diverse environments. However, because of genotype-by-environment interactions (G × E), it is difficult to identify a variety that would be accepted by most farmers on different islands. A new type of breeding programme with a pragmatic approach is therefore necessary. The geographical distribution of allelic diversity appears as a practical and cost-efficient solution.