Retinoids derived from Vitamin A have revolutionised the treatment of diverse skin diseases like psoriasis, ichthyosis and hyper keratosis since 1977. Their effect on the skin is as an antiphlogistic and antiproliterative. Skin diseases which respond to retinoids particularly well are, more often than not, those which take place over a lengthy period of time, often necessitating long term therapy. This is, unfortunately, all too often accompanied by a range of unwanted side-effects on the skin and body of the patient. Dermatological possibilities of use of retinoids are introduced with the help of actual literature and unwanted effects are listed in tabular form. These data are compared with own actual examinations of 90 patients observed over a period of 15 years. The most important results of our examinations show that retinoids are suited for a long term therapy, taking place over a period of years, and that even chronic skin diseases like psoriasis can be influenced positively within such a lengthy timescale. In the course of the retinoid therapy, 75 patients suffering from keratinization and 15 patients with severe forms of acne were treated successfully. In addition to the unwanted side-effects, including cheilitis, hair loss and increased susceptibility of skin to external noxes, we found paraclinical effects; increased blood fat, especially cholesterol and triglycerids, as well as an increase of liver enzymes. In rare cases, these effects can mean the patient has to reduce, or even discontinue, the treatment. It is, therefore, important to adapt the dose of retinoid to match the skin disorder. With this proviso, retinoids remain an extremely effective and controllable active agent in the treatment of chronic and genetic determinated skin diseases.