This article analyzes determinants of technology acceptance and their interdependence. It highlights the role of affect in attitude formation toward new technologies and examines how it mediates the influence of stable psychological variables on the technology’s acceptability. Based on theory and previous empirical evidence, we develop an analytical framework of attitude formation. We test this framework using survey data on attitudes toward stratospheric aerosol injection (SAI), a technology that could be used to counteract global warming. We show that affect is more important than risk and benefit perception in forming judgment about SAI. Negative and positive affect directly alter the perception of risks and benefits of SAI and its acceptability. Furthermore, affect is an important mediator between stable psychological variables—such as trust in governmental institutions, values, and attitudes—and acceptability. A person’s affective response is thus guided by her general attitudes and values.