Some chronic diseases have a favourable course and are cured spontaneously. Allergic diseases such as eczema, hay fever and asthma have a good outcome in more than 75% of cases within 7 to 25 years, depending on the kind of allergy. Migraines have also a good evolution in children and after menopause. Many symptoms due to menstruation such as dysmenorrhea, premenstrual syndrome or anemia, disappear after menopause as well as diseases due to estrogens such as uterine leiomyoma, endometriosis and prolactinoma. The risk of epilepsy relapse after a first seizure is about 40% after 2 years. The risk is lower in children. Attention deficit disorder affects 3 to 5% of children but is present in only 30% of them in adult age. The prevalence of depression decreases in women between 30 and 60 years of age. Functional somatic syndromes such as fibromyalgia, irritable bowel syndrome or dyspepsia decrease in 2/3 of cases within 5 to 10 years if there is no history of anxio-depressive symptoms. However, prognosis is reserved when initial symptoms are severe or if they are connected to sexual abuse, domestic violence or depression. Other diseases have a spontaneous favourable course such as myopia, idiopathic infertility, polycystic ovary disease or ventricular arrhythmia. The knowledge of a good prognosis enables to avoid unnecessary treatments and to reassure many patients.