The present work was developed in the cropping year 1996/97, at experimental area of FE/UNESP, located in Selvíria - Mato Grosso do Sul - Brazil (20º22?S, 51º21?W and 335m of altitude), with the objective of evaluating the dry matter accumulation weekly in different parts of plant (stem + branches, leaves, capsules of pods and seeds) from stadium R2, and physiologic quality of the soybean seeds, cultivar IAC-15, from R6 to 14 days after the stadium R8. The seeds were evaluated as the germination, vigor (electric conductivity, accelerated aging and weight of dry matter of seedlings), moisture content and weight of 1000 seeds. Seeds were obtained in the apex (last four knots with completely developed leaf) and in the base (remaining of the plant) of the sampling plants. It was verified that the dry matter accumulation in the soybean plants increased to the end of the period R6 (49 days after the beginning of the stadium R2); the seeds reached dry matter accumulation maximum in the stadium R7 and during the stadium R6 they were the main responsible for the growing dry matter accumulation whole plant; in general, the seeds obtained during the stadiums R6 and R7 presented better physiologic quality as the germination and vigor; the seeds obtained during the end of the stadium R6 and stadium R7, showed smaller weight, however, they provided seedlings with similar dry matter weight, compared with the seeds obtained in the stadium R8; seeds of the apex and of the base presented similar quality as the germination and weight of dry matter of seedlings; the seeds of the apex presented larger vigor than the one of the plant base, evaluated by the test of electric conductivity and accelerated aging, only during the stadium R6 of the plants. The moisture content of the seeds of apex and base and development stadium of plants in the samplings weekly from R6, were respectively: R6=70.8 and 71.1%, R6=67.2 and 67.9%, R6=64.0 and 63.3%, R7=48.8 and 54.7%, R8=15.0 and 15.6%, R8+7 days=17.3 and 19.4%, R8+14 days=13.2 and 13.5%.