Hirano No. 2 kofun is a round mound 6.5m high and with an estimated diameter of 26m, located in the Hirano district of the city of Kashiba, Nara prefecture, in the western part of the Nara basin. The stone chamber has remained buried from the Edo period on, and until now the existence of the chamber and the details of its shape have been uncertain. The current contribution is a preliminary report of the excavation of the horizontal stone chamber, conducted from 11 July 2000 through 30 March 2001 by the Kashiba municipal Nijosan Museum.<BR>Whereas no grave goods of note were recovered from the chamber interior, which had been robbed in the Medieval or Early Modern periods, from the method of piling the stones and the shape of the chamber, and from the artifacts that were found, the tomb is inferred to have been built in the mid-seventh century. The horizontal stone chamber of Hirano No. 2 kofun is characterized by a structure in which stones used for both the burial chamber and passageway are made from huge boulders of granite, and stood mostly with their long axes upright and nearly vertical. A base built with earth in the center of the burial chamber floor served as a podium for the coffin stand, and the entire floor area of the burial chamber was paved with hewn slabs of volcanic tuff obtained from Nijosan mountain, a burial chamber structure for which no previous examples are known for horizontal stone chamber tombs.<BR>On top of the earthen podium in the burial chamber was a coffin stand made with low-fired bricks and an earthenware frame, into which it is thought a coffin of wood or some other organic materials was rested; thus a singular arrangement has come to be inferred with regard to the manner of burial as well.<BR>The placement of a coffin stand within a burial chamber built with hewn slabs of volcanic tuff from Nijosan mountain was one of the burial chamber structures popular in the Final Kofun period of the Asuka region, in which burials in stone compartments with side entrances became the dominant form. The structure of the burial chamber of Hirano No. 2 kofun is thought to be a precursor which will be extremely important for considerations of Asuka period tombs in the future.