In general, where anxiety appears to have a specific external focus, such as the situations which are avoided by phobic patients, treatment involving systematic exposure to those situations seems to be effective. This is less appropriate, or even impossible, where anxiety is not dependent on any external circumstance, but is described by the patient as occurring at any time or place, either chronically over long periods, or acutely in the form of ‘panic attacks’. These patients with ‘generalised’ anxiety often describe internal cues for anxiety either in the form of thoughts (e.g. worry over a current problem) or somatic (e.g. chest sensations interpreted as possible heart disease). Beck et al. (1974) has suggested that on interview, all patients diagnosed as suffering from diffuse or generalised anxiety can report specific ideas or other cognitive cues which are associated with anxiety. These usually concern possible traumatic events, such as illness and death, or social rejection. Clearly Beck has in mind the possibility that these cognitions have the effect of inducing anxiety, although even if the validity of the subjective reports were to be accepted, the problem remains of whether the relationship between mood state and cognitions is causal and if so, in which direction it operates. Obviously a causal relationship may also operate in both directions simultaneously, to form a ‘vicious circle’ in which each exacerbates the other. To establish whether there is a sense in which particular cognitions contribute causally to anxious mood, it would be necessary to find a method of manipulating the type or frequency of cognitions thought to be operating in this way. One obvious possibility is that of ‘thought-stopping’: that is, patients could be taught to identify thoughts which are associated with anxiety and stop them in the usual way (Wolpe, 1973, p. 211) e.g. by' shouting stop, and substituting an alternative thought. The present study was planned as a pilot experiment to determine (i) if appropriate anxiety related cognitions could be elicited from a series of patients with generalised anxiety, (ii) if the reported frequency of such thoughts could be modified by a thought-stopping technique, and (iii) if any changes in thought frequency were associated with improvements in mood. Clearly there are many ‘non-specific’ features involved in thought-stopping which could also have therapeutic effects on mood. For this reason it was necessary to include an alternative procedure, not directed at reducing thought frequency, but having the same degree of plausibility to patients, and preferably to therapists. The control procedure chosen for this purpose was modelled on desensitisation, in which patients were encouraged to allow the supposedly anxiety-provoking thoughts into their mind and tolerate them, rather than attempt to stop them. In summary, the study employed a relaxation training phase as a base-line, followed by a cross-over design in which the two treatment phases of thought-stopping and ‘cognitive desensitisation’ were given to each patient, in balanced order.