The problem of origin and extension of the river terrace in Serbian valleys has been dealt with by many explorers. Beside those extensive investigations, this problem has not been explained enough. Therefore, more detailed investigations of river terraces were taken on a smaller region in the valley of the river Crni Timok in the basin of Zaječar (the Eastern Serbia). A series of low river terraces (the first terrace of r.h. 3-5 m the second terrace of r.h. 5-10 m, the third terrace of r.h. 10-16 m and the forth terrace of r.h. 20-30 m) and two special levels (inundation level of r.h. 0-2 m and the level of low shelves of r.h. 2-4 m) were set aside on this tract. This series of low river terraces of the river Crni Timok brought about the idea of the cyclic origin of some terrace series, which is to be tested by future explorations.