We tested several hypotheses derived from the emotional processing theory of fear reduction by manipulating claustrophobic participants' focus of attention during in vivo exposure. Sixty participants displaying marked claustrophobic fear were randomized to one of four exposure conditions. Each participant received a total of 30-min of self-guided exposure 2-weeks after pretreatment testing. One group attended to threatening words and images during exposure (TW) and was compared to a control group that attended to neutral words and images (NW). A third group performed a demanding cognitive load task--a modified Seashore Rhythm Test during exposure (SR) and was compared to an exposure only (EO) control group. Contrary to prediction, the threat word manipulation was not associated with lower levels of fear following treatment. Consistent with prediction, the distraction manipulation resulted in less fear reduction at post-treatment. Treatment process analyses revealed that the negative effects of distraction on treatment outcome manifested early as slower between-trial habituation. These results and their relevance to emotional processing theory are discussed.