Trichoscopy (or dermoscopy of hair and scalp) is an easy in-office technique that may be performed with a handheld dermoscope or a digital videodermoscopy system. This method is gaining increasing popularity, because it may be applied in differential diagnosis of multiple hair and scalp diseases. The focus of this article is application of trichoscopy in differential diagnosis of the most frequent hair and scalp diseases in dermatologic practice. Trichoscopy of genetic hair shaft abnormalities are briefly addressed. A new classification of perifollicular and interfollicular skin surface abnormalities is proposed.