This thesis introduces and defends a vulnerability theory of exploitation and uses that theory to explain what is exploitative about international transactions such as commercial gestational surrogacy and clinical trials. The vulnerability theory is preferable to a number of alternative theories of exploitation that have been defended in the philosophical literature. The dominant theories of exploitation tend to be inadequate or incomplete to account for different forms of exploitation. These shortcomings stem from the theories’ tendency to mistake something that is characteristic of specific forms of exploitation for what constitutes exploitation itself. Meanwhile, according to the vulnerability theory, exploitation occurs when A derives b...