Inhibition of growth of reproductive organs by high temperature may be involved in the occurrence of delayed stem senescence (DSS) of soybean. Six soybean cultivars were grown in the Temperature Gradient Chambers (TGC) and in a field adjacent to the TGC and yield components and degree of DSS were measured for individual plants. Four temperature plots (T1-T4) with mean temperatures from 23.1 (T1) to 25.8 (T4) °C) were established in the TGC when all cultivars reached the flowering stage. The number of perfect kernels per floret, single perfect kernel weight and seed yield were 13, 10 and 17% lower, respectively, in T4 than in T1. However, the effect of temperature on the occurrence of DSS was not evident. All the measurement values for each cultivar were pooled and individual plants of each cultivar were classified into DSS and non DSS groups. The mean values of the total floret number, pod set ratio, seed number per pod and perfect seed ratio were similar between the plants in DSS and non DSS groups in most cultivars, but the length of main stem, aboveground dry weight and seed yield were 15 to 28% greater in DSS than in non DSS group. In conclusion, the temperature a few degrees higher than usual during the reproductive period can inhibit development of sink organs but this may not be the primary cause of the occurrence of DSS in soybean.