Thought suppression is the attempted removal of unwanted thoughts. A plethora of previous research suggests that thought suppression is ineffective and possibly even counterproductive. However, the psychological processes involved in suppression are still underspecified. The current thesis aimed to examine the processes involved in thought suppression and to provide alternative techniques that may be more effective in the management of unwanted thoughts. To that end, Chapters 2 and 3 of the current thesis investigated the two key phenomena in the thought suppression literature, the immediate enhancement and rebound effects. Results from Experiments 1-4 indicated that participants, for the most part, found it difficult to suppress their thoughts during a five minute suppression phase, and also tended to have the unwanted thought re-emerge in a five minute phase following suppression, providing evidence for both the immediate enhancement and rebound effects. Chapter 4 (Experiment 5) provided a model of the immediate enhancement and rebound effects in terms of derived stimulus relations. The findings suggested that thought suppression attempts are ineffective due to the large number of intended and unintended environmental reminders. Experiments 6(a) and 6(b) extended on Experiment 5 by demonstrating how those relations might affect overt behaviour. Finally, Chapter 5 aimed to compare thought suppression with alternative strategies for dealing with unwanted thoughts. Acceptance and Commitment Therapy (ACT) was designed to undermine the negative behavioural consequences of derived stimulus relations. Experiments 7, 8 and 9 compared thought suppression with two components of the ACT model (i.e., mindfulness and defusion). The findings indicated, across both self report and behavioural measures, that the ACT techniques provided useful alternatives to thought suppression. In conclusion, the current thesis provides a behavioural model of the counterproductive nature of thought suppression whilst providing favourable evidence of alternative methods in the management of unwanted thoughts.