Evidence-based medicine combines the best currently available evidence from systematic medical research, together with clinical expertise, in order to provide the best available care for patients. In conjunction with systematic reviews (meta-analyses), a critical review of evidence-based literature forms the basis for the development of clinical treatment guidelines. Current treatment guidelines for generalized anxiety disorder (GAD) advocate the use of selective serotonin reuptake inhibitors (SSRIs) or serotonin-noradrenaline reuptake inhibitors (SNRIs) as the first line of pharmacotherapy. The safety and tolerability profiles of other medications, such as the benzodiazepines, limit their use, especially for long-term treatment. Since data comparing the efficacy in GAD of different SSRIs are limited, selection of one SSRI over another is generally based on consideration of tolerability profiles. Treatment guidelines for patients with social anxiety disorder (SAD) often recommend SSRIs as the first line of medication treatment, as this class has the largest evidence-base in support of efficacy. Less consistent evidence of efficacy exists for other agents, such as reversible inhibitors of monoamine oxidase inhibitor A (RIMAs), and issues of safety are a concern when considering the use of benzodiazepines. Again, there are few head-to-head studies of the SSRIs, and treatment selection is usually made on the basis of tolerability issues. The efficacy and tolerability of the SSRI, escitalopram, has been evaluated in patients with GAD and with SAD. In long-term studies of SAD, escitalopram demonstrated superior efficacy to placebo and paroxetine. It also exhibited a better tolerability profile, as assessed by discontinuation emergent signs and symptoms (DESS), in both patient groups. Furthermore, in relapse prevention trials of SAD, escitalopram conferred a significant benefit relative to placebo.