Development of Rice Core Collection. Tiur S. Silitonga and Andari Risliawati. Rice genetic resources have been collected from almost all of the district in the provinces of Indonesia. Presently, the collection of rice genetic resourses are totally 4.200 accessions. The purpose of these activities were to test, select and grouping of rice genetic resources to develop core collection. Various activities have been conducted such as characterization and selection of rice genetic resources to agronomic performance and yield, evaluation to brown plant hopper and grassy stunt virus and their resistance/tolerance to bacterial leaf blight, blast, and drought. Development core collection with various traits such as morphology and agronomy characteristics, yield component, seed quality, resistance to pest and diseases and tolerance to abiotic stresses will increase the use of rice genetic resources to create high yielding varieties with various traits. The availability of various rice varieties with traits needs could cover all the areas including lowland, upland, swampy areas, and marginal land areas with endemic attacked by pest and diseases. All rice genetic resources have been characterized to agronomic performance and yield in Sukamandi experimental farm, evaluated their resistance to brown plant hopper and bacterial leaf blight in Sukamandi and Cianjur, and drought tolerance in Jakenan, Central Java. The results of the experiment have developed core collection by grouping varieties with their traits such as 55 accession (accs.) of varieties with long panicle (>30 cm), 25 accs. short duration (<115 days), 32 accs. of dwarf plant (<115 cm), 25 accs. of short to medium duration (<130 days) with yielded 4.7-5.9 t/ha, 35 accs. have low to medium amylose content, 20 accs. resistant to brown plant hopper and grassy stunt virus, 33 accs. resistant to bacterial leaf blight, 23 accs. resistant to blast and 30 accs. tolerant to drought.