New Zealand regions have markedly different population dynamics. Population change in a region is driven by three different factors: fertility, mortality and migration. A fourth factor that is often related, momentum, is analysed in a separate paper (Pool et al. forthcoming-f). The present paper analyses the degree to which the levels and impacts of these three factors differ within New Zealand. It looks at regional dynamics by analysing growth and its components, natural increase (births and deaths) and migration, both domestic and international. We first present a review of population flows, and then disaggregate these into their components; natural increase and net migration, so as to provide a demographic accounting of the factors of change. The changes are investigated for the period 1986-2001 and then for the three quinquennia of 1986-91, 1991-96 and 1996-2001.