This paper reviews theories, current conditions, and barriers to liquidization and concentration of farmland in Japan and discusses perspectives on further research. We make special effort in introducing theoretical approach to understand institutional barriers to farmland liquidization, such as the farmland law system, compensation for tenants' investment, farmland transaction costs, and the high potential for farmland conversion. Since many of the studies in Japan on this topic are anecdotal or based on case studies, econometric studies from overseas that use detailed data are selectively reviewed for reference. Future studies should consider linkage and complementarities between anecdotal or case studies and quantitative approaches. Quantitative studies that test various hypotheses in debate are required. Use of farm or region level panel data should be useful and effective to take into consideration for identification of causality. Rigorous policy evaluations are also necessary for assessing and improving policies that promote structural adjustment.