Foeniculum vulgare Mill.(F.vulgare),commonly known as Fennel,is a popular medicinal plant with various pharmacological activities mentioned in traditional Iranian medicine(TIM) and modern phytotherapy such as antioxidant,cytotoxic,anti-inflammatory,antimicrobial,bronchodilatory,estrogenic,diuretic,lithontripic, galactogogue,emmenagogue,antithrombotic,hypotensive,gastroprotective,hepatoprotective,memory enhancing,and antimutagenic activities.No serious adverse events were recorded after ingestion of F.vulgare except some cases of allergic reactions.The estrogenic activity of F.vulgare brings some side effects such as decrease in protein concentration and acid and alkaline phosphatase in male genital organs,increase in weight of mammary glands and reproductive organs in women and premature thelarche in girls.However,no evidence of teratogenicity was recorded,it is better not to use F.vulgare during pregnancy due to its estrogenic activity.Because of inhibition of cytochrome P450 3A4(CYP3A4),the pharmacokinetic parameters of drugs mainly metabolized by this isozyme may be affected by F.vulgare.In addition,a significant interaction between cyprofloxacin and F.vulgare was demonstrated.The aim of current paper is to review pharmacological properties,toxicity and adverse events,and drug interactions of F.vulgare and brings conclusive results about the use of this plant in men,women and during pregnancy. Foeniculum vulgare Mill. (F. vulgare), commonly known as Fennel, is a popular medicinal plant with various pharmacological activities mentioned in traditional Iranian medicine (TIM) and modern phytotherapy such as antioxidant, cytotoxic, anti-inflammatory, antimicrobial, bronchodilatory, estrogenic , diuretic, lithontripic, galactogogue, emmenagogue, antithrombotic, hypotensive, gastroprotective, hepatoprotective, memory enhancing, and antimutagenic activities. No serious adverse events were recorded after ingestion of F. vulgare except some cases of allergic reactions. The estrogenic activity of F. vulgare brings some side effects such as decrease in protein concentration and acid and alkaline phosphatase in male genital organs, increase in weight of mammary glands and reproductive organs in women and premature thelarche in girls.However, no evidence of teratogenicity was recorded, it is better not to use F. vulgare during pregnancy due to its estrogenic activity. Cancer of inhibition of cytochrome P450 3A4 (CYP3 A4), the pharmacokinetic parameters of drugs mainly metabolized by this isozyme may be affected by F. vulgare. Addition, a significant interaction between cyprofloxacin and F. vulgare was demonstrated. The aim of current paper is to review pharmacological properties, toxicity and adverse effects events, and drug interactions of F. vulgare and brings conclusive results about the use of this plant in men, women and during pregnancy.