A guide to the trichoscopic diagnosis of the most common hair diseases. Rich in photographs, it allows immediate visualization of the trichoscopic signs, useful for a comparison with the real aspects observed during clinical practice. The pathogenesis of the various signs is indicated so that the reader is able to interpret the symptoms and the extent of the problem in the most appropriate way. It contains indications on the correct magnifications for optimal visualization of the hair, skin and vessels; and the usefulness of dry or interface trichoscopy. It is only with knowledge of the physiology and pathology of hair, and with practical experience, that one learns to diagnose and manage alopecia and trichoscopy helps in all three processes.