Randomised controlled outcome studies have demonstrated the comparable effectiveness of cognitive therapy and imaginal desensitisation (relaxation-based technique) in the treatment of pathological gambling. This study was undertaken in an attempt to determine if these treatments exert their therapeutic effect through common modes of action, either altering distorted cognitions or reducing arousal. A sample of twenty pathological gamblers were randomly allocated to one of two treatment groups: eleven to cognitive therapy and nine to imaginal desensitization, and a semi-structured interview, battery of psychometric measures and visual analogue scales, and heart rate measures were recorded at pre-treatment baseline, mid and end of therapy sessions and at one month follow-up. Consistent with other studies, there was a high rate of attrition (50%) with only ten completing the full course of treatment and six completing the follow-up assessment. The resulting small sample size due to attrition precluded adequate statistical analyses from being conducted on the data. However, results showed a tendency for the scores on the gambling beliefs questionnaire, a measure of irrational beliefs, to show a consistent decrease for the cognitive therapy group during treatment as compared to the imaginal desensitization group. Scores tended to stablize in that they did not show a continued decrease from end of treatment to followup. In respect to the treatment groups, visual analogue scale scores showed a consistent decrease in the urge to gamble and excitement associated with gambling across treatment for the cognitive therapy group. There was also a relatively consistent increase in perceived self-control from commencement of treatment to follow-up. In contrast, the imaginal desensitization group evidenced a consistent rise in perceived self-control over the course of treatment but this was not reflected in any change in level of urges or excitement experienced in response to gambling stimuli. This is contrary to expectations and the hypothesised mode of action for this form of treatment. 4 It is strongly emphasised that these are tentative findings but preliminary data seems to suggest that cognitive therapy is effective in reducing irrational beliefs with reductions in urges and excitement associated with such changes, while in contrast, imaginal desensitization is associated with an increase in self-control that is mediated by variables other than changes in subjective arousal or cognition. If these findings hold to be true with increased sample sizes and replication, targetting irrational cognitions directly may have a secondary effect on arousal, urges and excitement while the mechanism of imaginal desensitization does not operate through its hypothesised mode of action but is mediated through some other process that is yet to be established.