The purpose of this study was to investigate the process of change during three interventions for claustrophobia, with particular reference to cognitive changes. Forty-eight participants, recruited from the community through the local media, were randomly assigned to one of four groups: pure exposure, exposure to the sensations of anxiety (interoceptive exposure), modification of negative cognitions, or a control group. All interventions were given over three sessions. The exposure group proved superior to the control on a wide range of measures. In the cognitive group, scores of reported fear and panic, declined significantly. The interoceptive group made some modest gains. An analysis of the timing of fear reduction and of treatment generalization, provides some indications of the mechanism of change.