AbstractThe indigenous arid zone shrub Acacia victoriae grows rapidly and is relatively shortlived. The relationship between population structure, growth and mortality was examined by annual monitoring of over 1200 plants at twenty sites from 1978 to 1981. Sites were reassessed in 1992. Plants of similar size varied greatly in growth rate. Annual mortality ranged up to 16%. Of 752 plants alive in 1981, 206 (27%) survived until 1992. A transition matrix model, based on growth and mortality over the 3 year period, predicted a size‐class frequency distribution after 12 years that was significantly different from the one observed in 1992. The proportion of large plants present in 1992 was higher than predicted. The model's prediction that a large proportion of plants would remain in the lower size‐classes was reliable. We concluded that size is not a good indicator of age and that it is unreliable to identify cohorts of this species by examining size‐class frequency distribu