Publisher Summary This chapter describes the methods and mechanisms of chromosome banding. The chromosomes stained with quinacrine mustard and examined by fluorescent microscopy showed a distinct banding pattern and opened the field of chromosome banding. This Q-banding technique is a readily usable and reproducible technique to develop bands all along the chromosomes. Centromeric-type constitutive heterochromatin and a Giemsa banding procedure produce bands that mimic those seen with quinacrine. A modification of the G-banding procedure resulted in a pattern opposite to G-banding and this was termed R-banding. The chapter outlines some standardized methods for Q-banding, C-banding, R-banding, two techniques for G-banding, and describes the probable mechanism of these different techniques. None of the banding techniques work if the chromosome preparations are poor. The ideal chromosomes are those that are contracted just enough so that there is little problem with overlapping.