The detailed characterization of G-banding patterns of high resolution human chromosomes has been possible with the utilization of a refined cell synchronization technique which routinely yields a large number of excellent quality cells in late prophase, prometaphase, early metaphase, and mid-metaphase. The mitotic cells exhibit up to a 400% increase in the number of bands previously visualized by standard methods. From studies of the banding patterns, it has become evident that the G-positive and, to some extent, the G-negative bands of mid-metaphase results from a coalescence of finer subbands of earlier stages and that each band and its corresponding subbands maintain a constant location throughout the process of chromosome condensation. A precise schematic representation of the number, position, height and staining intensity of bands is presented for the five largest chromosomes of the complement at the four mitotic stages.