Therapeutics to treat or prevent anxiety are numerous but many people choose to try non-conventional medicine such as homeopathy. This study aimed at evaluating the effectiveness of Gelsemium 5CH and 15CH on provoked anxiety in healthy volunteers, in comparison with placebo. This was a double-blind, single-centre, randomized, placebo-controlled study. Eligible healthy men or women aged from 18 to 40 years without a history of psychiatric disorders were randomly allocated to receive Gelsemium 5 or 15CH or placebo. Anxiety was proved by performance of the Stroop colour word test (SCWT). The primary end-point was anxiety assessed by the State measure of the State-Trait Anxiety Inventory (STAI-S) as the absolute value and difference with baseline, according to the treatment received. We included 180 healthy volunteers. The distribution into each treatment group was homogenous. There was no statistical difference between groups for the values of STAI-S at baseline, just before the SCWT and the difference between these times (1.8 [0.20 to 3.4], 1.0 [−0.6 to 2.6] and 1.4 [−0.3 to 3.0] for Gelsemium 15CH, 5CH and placebo respectively). Likewise, no statistical difference was observed between groups in anxiety as measured by a Visual Analogue Scale and the Competitive State Anxiety Inventory. Mean arterial pressure and heart rate significantly increased (P < 0.001) but no interaction between time prior to provoked anxiety and treatment was shown (P = 0.59 and P = 0.46, respectively). Gelsemium 5CH and 15CH do not prevent anticipatory anxiety in the conditions used in this study.