Most tomato cultivars are F1 hybrids. Tomato breeding for the fresh produce market in Japan has focused on high quality (e.g., high sugar content), but the yields of Japanese F1 cultivars are generally lower than those of high-yield hybrids developed for mass-production hydroponic culture systems in Europe. To analyze the genetic factors that contribute to the yield and quality of tomato, we selected two F1 cultivars as parents and crossed them to establish the experimental populations. One parent was the Japanese F1 cultivar ‘Momotaro 8’ (Takii & Company, Ltd., Japan), which is characterized by high sugar content, and the other was the high-yield Dutch F1 cultivar ‘Geronimo’ (De Ruiter Seeds, the Netherlands). This cross corresponded to a four-way cross, as the four parental lines of the two F1 cultivars were considered to be the founders. We generated an F1 population consisting of 240 plants by crossing the two cultivars and each F1 plant was subjected to additional cycles of selfing with single-seed descent to generate recombinant inbred lines (RILs). Genotyping data of F6 RILs using more than 200 genome-wide simple sequence repeat (SSR) markers were subjected to the construction of linkage map. Results of QTL analysis in RILs at F6, F7 and F8 generations are reported. Acknowledgements. This work was supported by grants from the Ministry of Agriculture, Forestry and Fisheries of Japan (Genomics for Agricultural Innovation, SGE1002).