ABSTRACT: The effect of temperature and population density on the growth of Atlantic herring Clupea harengus was studied using a comparative approach applied to 15 North Atlantic populations. The von Bertalanffy (VB) equation was applied to describe mean growth of individuals in each population, both averaged over the whole period studied and for each cohort. Water temperature was a determinant factor for herring growth at the species level: North Atlantic herring in cold water areas exhibited a lower growth coefficient (k), longer lifespan and a higher asymptotic weight (w_inf) than those living in warmer water. The average w_inf of herring was positively correlated to the density of biomass of that population. This relationship was most likely due to the negative correlation found between population density and mean temperature. At the within-population level, when looking at the temporal variability in growth parameters amongst cohorts, w_inf was still negatively correlated to temperature, but the positive correlation between k and temperature was no longer significant. In a single population, the temperature range is probably too narrow to have an identifiable effect on growth. The effect may be confounded by other factors such as density dependence. On the basis of this macroecological pattern, global warming should enhance growth of the youngest age-classes, but reduce the growth of older individuals and shorten the lifespan of herring.