1. The physical and behavioral characteristics and the temporal patterning of musth were studied over a ten-year period in a free-ranging population of African elephants. 2. Males spent more time in association with females during musth than during non-musth periods. 3. Males were more aggressive during their musth periods than during non-musth. 4. The occurrence and duration of musth were age-related: no male under 24 years was seen in musth; bouts of must among younger individuals were short and sporadic, while older males experienced longer more predictable periods of musth on an annual basis. 5. Although males in musth were observed year-round, the frequency of musth males was highest during and following the two rainy seasons and, in general, good rainfall years had higher frequencies of males in musth than did poor rainfall years. 6. The number of males in musth per month correlated closely with the number of females observed in estrus. However, since the period of estrus lasts only four to six days (Moss, 1983), while musth may last several months, the onset of musth was not necessarily triggered by the onset of estrus in a particular female. 7. The musth periods of different males were asynchronous and each male came into musth at a specific time of year. This period was relatively consistent from one year to the next, particularly among the older males. 8. Males in musth advertised their heightened sexual and aggressive state through visual and olfactory signals and by vocalizing. It is suggested that these signals function to announce identity, condition and location to both rival males and to potentially receptive females. 9. The physical and behavioral characteristics and temporal patterning of musth in African and Asian elephants are compared and found to be remarkably similar. 10. The physical and behavioral manifestations of musth in elephants are similar to those described for other male mammals during rut. Since estrus in female elephants is less clumped relative to most ungulates, male elephants have a different temporal pattern of rutting. Although the musth periods of male elephants are asynchronous the phenomenon can functionally be considered a rutting period.