Soybean (Glycine max. L) is a legume which is recognised as being very nutritious and a very important food source. Champasack province is the biggest soybean producing province in Laos, especially in Bachiengchalernsouk district. However, despite a high level of production, grain yields under farming conditions are low. Higher yielding varieties need to be identified and introduced to farming communities in the area. In this study, the yield performance of ten promising lines and eight commercial varieties were evaluated and compared with a local variety. An on-farm, farmer participatory evaluation trial was conducted in Nongbokyai village Bachiengchalernsouk district, Chamapasack province. A similar evaluation of the lines and varieties was undertaken at the Maize and Cash Crop Research Center (MCRC) in Vientiane Capital. The experiment conducted in farmers fields in Bachiengchalernsouk district of Champassak province compared the performance of the breeding lines and varieties for two different sowing times, the first sowing being in early May 2016, and the second in early  September 2016. The experiment conducted at MCRC involved only one sowing date, midJuly 2016. The yield data collected during the study showed significant differences (P<0.01) among  the 19 test accessions for sowing date and location, for all the plant traits measured (maturity time, plant height, pods/plant, 100 seed weight and grain yield). Accessions ARC2007-P4-13, Yuanda10, Yuanda26, DT26, ARC1 and SJ5 showed good adaptability to farmer’s growing  conditions in Bachiengchalernsouk district, with grain yields ranging from 3% to 70% (70 to 1,200 Kg/ha) higher than the local control variety. Breeding lines ARC2007-P3-13-1,  ARC2007-8-10-11-12-12-1-P1-2-3, SJ5, CM60 and ARC2 showed yield stability (about 1,500 Kg/ha) despite the low fertility of soils in the on-farm location. Accessions ARC2007-P4-13 and Yuanda10 were rated as having the greatest potential for future release as new improved varieties, while variety DT26 also showed good adaptation to farmers’ conditions, suggesting that it could be considered for immediate released to improve farmer’s grain yields

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