Estradiol is the major steroid hormone which is involved in several organic functions, such as physiological sexual behaviour, development and maintenance of male and female reproductive organs, control of visceral secretion, modulation of immune system, and tumorigenesis. In this compilation, the authors discuss the synthesis, health effects and drug interactions of estradiol. Topics include the occurrence of estradiol in environmental waters; estradiol in the central nervous system and its role in neurodegeneration; the effects of estradiol on male and female reproductive tissues and the influence of endocrine disruptors; estradiol and prostate cancer; hydroxyestradiols and methoxyestradiols as endogenous factors associated to physiological and physiopathological conditions; oestrogen and functional gastrointestinal disorders; estradiol and memory; estradiol in the environment; use of combined therapy of estrogens with antidepressants; oestrogen and nitric oxide as a treatment for diabetes gastroparesis; estradiol synthesis after ovarian tissue cryopreservation and transplantation; estradiol-mediated overmodulation of the neuroendocrine hormone dopamine is central to the pathophysiology of restless leg syndrome during pregnancy; and oestrogen modulation on oxidative stress and synaptic plasticity in the dorsal hippocampus.