This article is concerned with the economic effects of immigration. The emphasis is on Britain, but extensive material is also provided on other countries. Since 1997 a new British immigration policy has displaced previous policy aims, which were focused on minimizing settlement. Large-scale immigration is now seen as essential for Britain's economic well-being, and measures have been introduced to increase inflows. The benefits claimed include fiscal advantages, increased prosperity, a ready supply of labor, and improvements to the age structure. Fears that large-scale immigration might damage the interests of unskilled workers are discounted. This article examines these claims. It concludes that the economic consequences of large-scale immigration are mostly minor, negative, or transient, that the interests of more vulnerable sections of the domestic population may well be damaged, and that any economic benefits are unlikely to bear comparison with immigration's probable substantial and permanent demographic and environmental impact. Our claims are in line with those from other developed countries.