Copyright © 1999 Academic Press Limited All rights of reproduction in any form reserved Growth performance and mortality are two topics related closely to population dynamics of benthic macroinvertebrates. A new measure of overall growth performance for benthic invertebrate populations, the index ψ = log(maxirnum body mass/maximum age) is introduced. This index makes growth of populations and species comparable and is likely to be a species-specific feature. Differences in the index <f> among taxa and living modes as well as the relationship between growth performance and exploitation by man are analysed and discussed. Section 4 on mortality analyses the relationships between mortality and productivity in benthic invertebrate populations. An empirical model to estimate the natural mortality rate M of benthic populations from maximum body mass, maximum age and water temperature is constructed. (G): general (T): temperature data (C): conversion factors (D): population dynamics.