Alexithymia has been defined as difficulty identifying and expressing emotions and an externally oriented mode of thinking. Previous research has linked alexithymia with somatoform symptoms yet there is little prospective data examining the role of alexithymia in somatization disorder. Thus, changes in alexithymia were examined over the course of a 10-session controlled trial of cognitive behavioral therapy for somatization disorder. It was predicted that the treatment would lead to reductions in alexithymia not seen in the group whose physicians received only a psychiatric consultation letter (PCL) and that CBT participants would score significantly lower on alexithymia than PCL participants. It was also hypothesized that changes in alexithymia from pre- to post-test, assessed through the Toronto Alexithymia Scale (TAS-20), would predict improvement in somatization symptoms, as assessed through the Clinician's Global Impression Scale for Somatization Disorder (CGI-SD) at post-test and at 12-month follow-up. Daily symptom diaries and physical functioning, assessed through the MOS-PF, were also examined as outcomes. Participants were 84 individuals diagnosed with full somatization disorder according to the DSM-IV. Baseline severity and post-treatment mental health, defensiveness, and somatosensory amplification were controlled for in regression analyses. Results partially supported hypotheses. Participants in the CBT condition decreased more in the TAS-20 and the DIF domain and marginally more in the EOT domain over the course of the study than participants in the PCL condition. They differed significantly from PCL participants at post-treatment in the EOT domain but not in the full scale TAS-20 or in any other domains. There were no significant differences between groups in alexithymia at follow-up. Decreases in alexithymia were significantly correlated with improvement in somatization symptoms and greater physical functioning. Although decreases in alexithymia significantly predicted certain outcomes at post-treatment and follow-up over and above control variables, tests for mediation yielded non-significant results. Findings from the current study support emotional functioning as a factor in somatization but do not advance the notion of alexithymia as a mediator of improvement in treatment for somatization disorder. Implications and suggestions for future areas of research are discussed.