These studies on indigenous ecological knowledge were carried out as a case study of the sustainability of miang tea gardens in hill evergreen forest at a remote village setting in the highlands of northern Thailand. The study focused on the miang tea farmers' knowledge associated with decision making criteria in managing their gardens as an agroforestry system. Knowledge was investigated relating to how farmers presently manage their garden ecosystems and the underlying biodiversity of the plants and the interactions occurring between tea trees and biotic components. These were forest trees, ground flora and cattle in relation to microclimate and processes of water and nutrient cycling, soil erosion and plant succession. The knowledge acquired from key informants was evaluated in terms of its representativeness of the knowledge of the community as a whole and the extent to which it was complementary or contradictory to scientific knowledge. The extent to which indigenous and scientific knowledge could be usefully combined was investigated. The indigenous knowledge was collected from interviewing a small number of key informants who were representative of the target popUlation and who were people knowledgeable about the ecology of the gardens. The elicited information was recorded and accessed using knowledge-based system techniques. An indigenous knowledge base was created in terms of diagrams, hierarchies and text statements and stored in a durable, accessible and transparent form. The research demonstrated that the indigenous ecological knowledge collected from key informants was explanatory, predictive and of technical relevance. It was also representative of most of the farmers in the community. The combination of indigenous and scientific knowledge provided a more powerful resource for improving the sustainability of the tea garden ecosystem than using either knowledge system alone but required further quantification for solid management recommendations to be formulated. The knowledge elicited had a useful role to play in furthering scientific understanding about the ecosystem and suggested new lines of research that may be more appropriate for promoting incremental change to miang tea production systems than extending conventional technology packages involving tea monoculture.