Emotions play an important role in human-computer interaction (HCI). Central to the design of some future computer systems are the questions of how emotions can be specified, expressed, and accounted for by machines. Drawing on social psychology research, a two-factor model for emotion in HCI is proposed. This model was tested with a laboratory study of emotions in HCI. A project is currently underway to build a system that demonstrates how this model can inform the design of computer interfaces.