the occurrence of green soybean seed due to forced maturation or premature plant death caused by drought or foliar and/or root diseases has been common in several brazilian production areas. physiological quality of seed lots with green seed may have their germination and vigor potentials affected and therefore discarded by the grain industry. the objective of this experiment was to determine the maximum tolerated level of green seed in soybean seed lots, which is information of major importance for seed producers when taking the decision whether to sell these lots. soybean seed of the cultivars cd 206, produced in ubirata, parana, and ？fmt tucunare,？ produced in alto gar？as, mato grosso, were used in the study. green seed and yellow seed of both cultivars were mixed in the following proportions: 0%, 3%, 6%, 9%, 12%, 15%, 20%, 30%, 40%, 50%, 75% and 100%. seed quality was evaluated by the germination, accelerated aging, tetrazolium and electrical conductivity tests. the contents of a, b and total chlorophyll in the seed were also determined. a complete randomized block design in a factorial scheme (two cultivars x 12 levels of green seed) was used. seed quality was negatively affected and chlorophyll contents incremented with the increase in the percentage of green seed. seed germination, viability and vigor, measured by the accelerated aging test, were not reduced with levels of up to 3% green seed, for both cultivars. levels above 6% green seed significantly reduced the quality of the seed. the quality of seed lots with 9% or more green seed was significantly reduced to the point that their commercialization is not recommended.