Due to its importance as a staple food and its role as the main source of income of approximately 18 million household farmers in Indonesia, rice production and availability are very much connected with the issue of national food security. Decreasing productive lowland area and large availability of upland area gives one possibility to increase rice production through developing high yielding upland rice cultivars. On the other side, lack of protein consumption is also an important problem. In Indonesia and several Asian countries, rice contribute less than 37.7 % of protein intake, especially in the rural area. The advantage of protein from rice is high digistability, non alergenic, and may be the only protein source with hypoalergenic. Furthermore, protein from rice also has fiber suitable for digestion and reducing colesterol (Tobiason, 2006). Therefore, it is important, to develop high yielding upland rice cultivar with high grain protein content. In a line with efforts to fulfill the needs of food and nutrition, Laboratory of Plant Breeding and Biotechnology, Faculty of Agriculture, Jenderal Soedirman University, Central Java, Indonesia has been developed new upland rice lines with high yield and high grain protein content through hybridization between several parental: high-yielding upland rice, tolerant to drought, Indica and Javanica type with low-land aromatic rice with high grain protein content (G 39 x Mentik Wangi, G 39 x Milky Rice, Ciherang x Milky Rice, and Ciherang x Milky Rice). Based on these sustain researches, some genetic information during the assembly of high yielding upland rice with high protein content were obtained. It informs its segregation pattern (in F2 generation), its gene action based on halfdiallel analysis, and also genotype x environment interaction. Grain protein content in F2 populations from Ciherang x Milky Rice hybridization is controlled by two duplicate recessive epistatic genes with 9:7 ratio. Grain protein content caracter in upland rice was determined by epistatic gene effect. Genotype x location interaction influenced grain protein content of upland rice indicating that the expression of genotypes were vary at different locations. This finding might be very useful to support food security and improve nutritional status of people in Indonesia and other country which has semiarid areas with low rainfall.