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Reproductive and aerial tillering dynamics in Lolium perenne L. (perennial ryegrass) was monitored for two years under grazing. Reproductive tillers were observed from winter (June) to midsummer (February) with the main period of initiation occurring in spring to early summer (August to October). For infrequent lenient grazing, reproductive tiller densities ranged from 102 (July 1993) to 1 900 (September 1993) tillers m−2, and from 29 (June 1994) to 980 (September 1994) tillers m−2. By contrast, simulated continuous grazing (CG) resulted in reproductive tiller densities ranging from 13 (August 1993) to 100 (October 1993) tillers m−2, and from 25 (July 1994) to 46 (September 1994) tillers m−2. Aerial tillers were initiated mainly during spring, and to a lesser extent autumn and winter, with no appreciable number being recorded during summer. For infrequent lenient grazing, aerial tiller densities ranged from 25 (February 1993) to 1 620 (September 1993) tillers m−2, and from 362 (August 1994) to 1 524 (September 1994) tillers m−2. By contrast, CG resulted in aerial tiller densities ranging from 123 (May 1993) to 14 (June 1993) tillers m−2, and from 5 (July 1994) to 29 (May 1994) tillers m−2. There was no indication that reproductive or aerial tillers contribute to the persistence of perennial ryegrass under the grazing frequencies and intensities tested.