1) This investigation was undertaken to determine the developmental process of the tillering primordium and tillering bud in rice seedlings. 2) Rice seedlings used in this study were nursed in sand culture from the sowing to the stages of the third foliage leaf, and after then in water culture. Harvested samples were fiked in mixtured fluid of Formalin, Acetic-acid and Alcohol, and microscopic examinations were carried out whether the samples were made of paraffin sections or were anatomized by hand. 3) The results of this investigation are summarized as follows. a) The differentiation of the tillering primordium and tillering bud in rice plant, except the axil of the coleoptile, were seen at the axils of all the foliage leaves. b) The differentiation of the first tillering primordium is seen about 0.5∼1.0cm in length of plumule, and in this stage the differentiation of the 4 th main leaf is observed. The differentiation of the second -(8 th tillering primordia) are seen about the stage of the first∼7 th main leaves. And ih these stages, respectively the differentiation of the 5 th∼11 th main leaves are observed. c) The shape of the early differentiating stage of the tillering primordium is semi-spherical form, and in this stage the central core of tillering primordium is surrounded by the rudimentary dermatogen of a layer (Fig. 1). According to the development of the tillering primordium, the prophyll differentiation of tillering appears at the circuit of their upper parts, and the prophyll grows like surrounding the growing point of the tillering primordium, (Fig. 2) and at last it forms the tillering bud of peach shape. d) The developmental process of the tillering primordia and tillering buds were shown in Table 1.