Corticosteroids are a class of steroid hormones which are mainly produced in the adrenal cortex of the vertebrates but are also synthesized artificially. They ease redness, itching, swelling and allergic reactions. There are two main classes of corticosteroids that are involved in a wide range of physiological processes. These two classes are glucocorticoids and mineralocorticoids. Glucocorticoids have immunosuppressive, anti-inflammatory, vasoconstrictive and anti-proliferative effects, and they also affect carbohydrate and fat metabolism. Mineralocorticoids mainly regulate water and electrolyte balance by modulating ion transport. Some examples of naturally occurring steroids are aldosterone, corticosterone, cortisone and cortisol. This book presents the complex subject of corticosteroids in the most comprehensible and easy to understand language. Its objective is to give a general view of the different classes of corticosteroids. The topics covered in this book offer the readers new insights in this field.