This paper assesses the consequences of immigration for natives' unemployment in OECD countries and investigates the role played by product and labour market policies in the economy's adjustment to immigration inflows. The estimations, combining a skill-level and an aggregate approach using data for males, cover eighteen OECD countries over the period 1984-2003. While no significant long-run impact is found, an increase in the share of immigrants in the labour force is estimated to raise temporarily natives' unemployment, over a period of approximately five to ten years. Anticompetitive product market regulations are found to increase both the magnitude and the persistence of this impact, while more stringent employment protection legislation magnifies its persistence, and a higher average replacement rate of unemployment benefits increases its magnitude.