BACKGROUND There is a lack of basic knowledge on the part of both clinicians and patients as to the indications for use and safety of herbs used during pregnancy and lactation. This is one article in a series that systematically reviews the evidence for herbs commonly used during pregnancy and lactation. OBJECTIVES To systematically review the literature for evidence on the use, safety and pharmacology of chastetree, focusing on issues pertaining to pregnancy and lactation. METHODS We searched 7 electronic databases and compiled data according to the grade of evidence found. RESULTS In pregnancy, there is poor evidence based on theoretical and expert opinion and in vitro studies that chastetree may have estrogenic and progesteronic activity, uterine stimulant activity, emmenagogue activity and prevent miscarriages. In lactation, theoretical and expert opinion conflict as to whether chastetree increases or decreases lactation. CONCLUSIONS Given its relatively common use amongst women of childbearing age, it is likely that some women may consume chastetree while unknowingly pregnant. Complementary and alternative medicine, midwifery and medical practitioners should be aware of this fact when prescribing chastetree to women of childbearing age, particularly when the patient is planning a family. Key words: Chastetree, vitex agnus-castus, pregnancy, lactation, breastfeeding, systematic review.