Rapid urbanization is a major cause of structural change in food demand. In West Africa, urbanization is associated with a switch from coarse grains to rice and wheat, in Melanesia the switch is from root crops to rice and wheat, while in much of Asia the switch is away from cereals (and within cereals to wheat). Although reasons why urban diets differ from traditional rural diets are well known, the rate at which recent arrivals from the countryside switch their diet has not been estimated. Evidence on the speed of this dietary change can help to show whether studies of urban food demand need to control for cohort effects and may also help producers forecast the size of their future urban markets. This paper uses cross-sectional household survey data from urban areas of Papua New Guinea to estimate the rate at which migrant household’s switch their diets from traditional root crops to imported rice and wheat products.