Dynamic recrystallization (DRX) in copper polycrystal was investigated in compression at 873 K and at a true strain rate of 2.9 x 10(-4) s(-1). The peak strain in the flow curve, where DRX macroscopically and frequently started to take place, was about 0.08. However, DRX had already started preferentially and locally at the triple junctions (TJs) at much lower strains from 0.02 to 0.04. The number of the DRX nucleation at the TJ increased linearly with increasing strain. At a strain of = 0.04, DRX took place at about 40% of the TJs. However, DRX nucleation seemed to be difficult when TJ was composed of twin boundary. It was also notable that most of the nucleated grains at the TJs kept twin ( 3) relation with one of the grains composing the TJs. This should be suggestive of the origin of the DRX grain. The DRX nucleation at the TJ and twin formation will be discussed in relation with grain-boundary sliding, grain-boundary migration, misorientation angle and etc.