This study was performed to investigate the anxiolytic efficacy of silexan, a new oral lavender oil capsule preparation, in comparison to placebo in primary care. In 27 general and psychiatric practices 221 adults suffering from anxiety disorder not otherwise specified (Diagnostic and Statistical Manual of Mental disorders-IV 300.00 or International Statistical Classification of Diseases and Related Health Problems, Tenth revision F41.9) were randomized to 80 mg/day of a defined, orally administered preparation from Lavandula species or placebo for 10 weeks with visits every 2 weeks. A Hamilton Anxiety Scale (HAMA) total score >or=18 and a total score >5 for the Pittsburgh Sleep Quality Index (PSQI) were required. The primary outcome measures were HAMA and PSQI total score decrease between baseline and week 10. Secondary efficacy measures included the Clinical Global Impressions scale, the Zung Self-rating Anxiety Scale, and the SF-36 Health Survey Questionnaire. Patients treated with silexan showed a total score decrease by 16.0+/-8.3 points (mean+/-SD, 59.3%) for the HAMA and by 5.5+/-4.4 points (44.7%) for the PSQI compared to 9.5+/-9.1 (35.4%) and 3.8+/-4.1 points (30.9%) in the placebo group (P<0.01 one-sided, intention to treat). Silexan was superior to placebo regarding the percentage of responders (76.9 vs. 49.1%, P<0.001) and remitters (60.6 vs. 42.6%, P=0.009). Lavandula oil preparation had a significant beneficial influence on quality and duration of sleep and improved general mental and physical health without causing any unwanted sedative or other drug specific effects. Lavandula oil preparation silexan is both efficacious and safe for the relief of anxiety disorder not otherwise specified. It has a clinically meaningful anxiolytic effect and alleviates anxiety related disturbed sleep.