Our main thesis is that the U.S. has a duty of justice to adopt an open border policy with regard to economic migrants because it is significantly responsible for the unjust social and economic conditions that bring such migrants to its borders. From this perspective, President Bush’s recent “guest worker” proposal is morally objectionable because it is designed more to serve U.S. business interests than the interests of the migrants. We address three objections to opening borders: it will worsen the economic condition especially of low-skilled native workers; it will harm developing countries by increasing the so-called “brain drain”; and it is preferable to discharge our responsibility to the global poor by increasing development assistance instead of adopting an open borders policy.