During mitosis and meiosis, chromosomes are distributed to daughter cells in controlled fashion, with patterns of chromosome distribution determined by specific interactions between chromosomes and the microtubules composing the spindle. In meiosis, for example, homologous chromosome pairs (bivalents) attach to the spindle so that the kinetochore of one chromosome of the pair is associated with kinetochore microtubules extending toward one spindle pole while the kinetochore-associated microtubules of the partner chromosome extend toward the opposite pole. This arrangement assures that partner chromosomes proceed in opposite directions during anaphase chromosome movement and results in the delivery of only one member of the homologous chromosome pair to each daughter cell. This sort of descriptive/mechanical account of mitotic and meiotic chromosome behavior is now well-established. However, total understanding of the role of the spindle in precise chromosome distribution demands a much more detailed analysis of spindle organization than is yet available. For instance, determination of where and how the innumerable microtubules of the spindle are mechanically linked should help to clarify exactly where forces for chromosome movement are applied.