In this paper the potential clinical applications for the human fetal estrogen estetrol (E(4)) are presented based on recently obtained data in preclinical and clinical studies. In the past E(4) has been classified as a weak estrogen due to its rather low estrogen receptor affinity. However, recent research has demonstrated that due to its favorable pharmacokinetic properties, especially the slow elimination and long half-life, E(4) is an effective orally bioavailable estrogen agonist with estrogen antagonistic effects on the breast in the presence of estradiol. Based on the pharmacokinetic properties, the pharmacological profile and the safety and efficacy results in human studies, E(4) seems potentially suitable as a drug for human use in applications such as hormone replacement therapy (vaginal atrophy and vasomotor symptoms), contraception, osteoporosis and breast cancer.