The long-range organization of arrays of alpha satellite DNA at the centromeres of human chromosomes was investigated by pulsed-field gel electrophoresis techniques. Both restriction-site and array-length polymorphisms were detected in multiple individuals and their meiotic segregation was observed in three-generation families. Such variation was detected in all of the alpha satellite arrays examined (chromosomes 1, 3, 7, 10, 11, 16, 17, X, and Y) and thus appears to be a general feature of human centromeric DNA. The length of individual centromeric arrays was found to range from an average of approximately 680 kilobases (kb) for the Y chromosome to approximately 3000 kb for chromosome 11. Furthermore, individual arrays appear to be meiotically stable, since no changes in fragment lengths were observed. In total, we analyzed 84 meiotic events involving approximately 191,000 kb of alpha satellite DNA from six autosomal centromeres without any evidence for recombination within an array. High-frequency array length variation and the potential to detect meiotic recombination within them allow direct comparisons of genetic and physical distances in the region of the centromeres of human chromosomes. The generation of primary consensus physical maps of alpha satellite arrays is a first step in the characterization of the centromeric DNA of human chromosomes.