This review and metachronanalysis was prompted by the presence of a circasemiseptan pattern (P < 0.05) found by population-mean cosinor in published data characterizing murine malignant growth after treatment with cyclophosphamide (1-4). For cancer chronotherapy (5-9), the analyses serve to suggest the desirability to extend the focus beyond circadian aspects of drug timing and drug effect to a broader view that takes into account as much of the body's make-up in time as is practical. Among the different components of a chronome (the time structure of rhythms with different frequencies and trends in a given variable), the 3.5-day patterns (circasemiseptans) and the 7-day patterns (circaseptans) are more readily accessible to measurement and thus to manipulation and optimization than infradians with even lower frequencies; they may also be pertinent to the scheduling of infusions covering several days, particularly those using drug administration devices, some of which are programmable. Should circaseptans and circasemiseptans characterize the host as well as the tumor, the drug administration schedule could be optimized for both treatment efficacy and host tolerance, with a view of infradian as well as of circadian and ultradian rhythms.