Repeated sequences are found ubiquitously in the eukaryotic genome. Population genetic studies on the evolution of such repeated sequences are reviewed while paying special attention to those sequences found in the non-coding regions of the genome. Specifically, the evolution of dispersed repeated sequences by the transposition as well as the evolution of short tandemly repeated sequences due to either replication slippage or unequal sister chromatid exchange are considered. The approach of combining both model and data analyses which has been successfully employed in the development of the neutral theory is also considered to be useful in better understanding the evolution and biological meaning of these sequences.