(1) Summer populations of the rose-grain aphid, Metopolophium dirhodum (Walker), were monitored in Bedfordshire (1978-80). Population density, age structure and distribution were studied by detailed sampling, and immigration and population development in different years are compared. (2) Population growth rates (intrinsic rates of increase and multiplication rates per week) are compared and contrasted with development temperatures. (3) The rate of spread of the population (the percentage of tillers infested related to aphid density) was the same function in each year. (4) Seasonal changes in feeding site distributions are given for 1979. The highest percentage of the total population occurred on flag leaves, and adaxial (upper) leaf surfaces were favoured. (5) Dislodgement of aphids by wind gusts appeared to be an important mortality factor. Rainfall (alone) was not a factor. Parasitism was greatest in 1978, but did not appear to be a controlling factor. Coccinellid predation appeared to limit population growth in 1978, and to severely reduce population density in 1980. (6) Maximum aphid densities varied enormously. The determining factors were growth regulated by temperature, in opposition to wind gusts, predators and parasites.