Vitex agnus castus L. (VAC) [Verbenaceae] is a deciduous shrub that is native to Mediterranean Europe and Central Asia. Traditionally, VAC fruit extract has been used in the treatment of many female conditions, including menstrual disorders (amenorrhoea, dysmenorrhoea), premenstrual syndrome (PMS), corpus luteum insufficiency, hyperprolactinaemia, infertility, acne, menopause and disrupted lactation. The German Commission E has approved the use of VAC for irregularities of the menstrual cycle, premenstrual disturbances and mastodynia. Clinical reviews are available for the efficacy of VAC in PMS, cycle disorders, hyperprolactinaemia and mastalgia, but so far no systematic review has been published on adverse events or drug interactions associated with VAC. Therefore, this review was conducted to evaluate all the available human safety data of VAC monopreparations. Literature searches were conducted in six electronic databases, in references lists of all identified papers and in departmental files. Data from spontaneous reporting schemes of the WHO and national drug safety bodies were also included. Twelve manufacturers of VAC-containing preparations and five herbalist organisations were contacted for additional information. No language restrictions were imposed. Combination preparations including VAC or homeopathic preparations of VAC were excluded. Data extraction of key data from all articles reporting adverse events or interactions was performed independently by at least two reviewers, regardless of study design. Data from clinical trials, postmarketing surveillance studies, surveys, spontaneous reporting schemes, manufacturers and herbalist organisations indicate that the adverse events following VAC treatment are mild and reversible. The most frequent adverse events are nausea, headache, gastrointestinal disturbances, menstrual disorders, acne, pruritus and erythematous rash. No drug interactions were reported. Use of VAC should be avoided during pregnancy or lactation. Theoretically, VAC might also interfere with dopaminergic antagonists. Although further rigorous studies are needed to assess the safety of VAC, the data available seem to indicate that VAC is a safe herbal medicine.