Worry exposure (WE) is a core element of cognitive-behavioral treatment for generalized anxiety disorder (GAD). Its efficacy as a stand-alone treatment method (without further cognitive-behavioral therapy interventions) has never been tested.We aimed to examine whether WE alone is as efficacious as the empirically supported stand-alone treatment for GAD, applied relaxation (AR). In a randomized controlled study, 73 outpatients meeting DSM-IV criteria for GAD as primary diagnosis were allocated to either WE or AR or a waiting list control group; in a 2nd randomization procedure the waiting list subjects were reallocated to WE or AR. The treatment was manualized (15 sessions with WE or AR), included 6-month and 1-year follow-ups, as well as last observation carried forward and completer analyses, and was controlled for allegiance effects.The Hamilton Anxiety Rating Scale and the State-Trait Anxiety Scale were used as primary outcome measures. Self-report scales of anxiety, worrying and depression including negative metacognition about worrying and thought suppression served as secondary outcome measures. The dropout rate was moderate. The pre-/posttreatment effects were high for the Hamilton Anxiety Rating Scale (standardized mean difference >1) and for the State-Trait Anxiety Inventory (standardized mean difference >0.87). The proportion of patients reaching high end state functioning was 48% (WE) and 56% (AR). WE and AR did not differ with regard to dropout rate or treatment effects. The treatment effects were stable at 6 month and 1 year follow-up. This is the first study to show that a stand-alone exposure in sensu technique--WE--is efficacious in the treatment of GAD. Both AR and WE seem to represent effective principles of change in GAD. 2009 S. Karger AG, Basel.