This document provides clinical decision trees to help diagnose 3 common hair abnormalities: alopecia (hair loss), hirsutism (excessive hair growth), and trichotillomania (hair pulling disorder). The first decision tree asks if the patient is experiencing hair loss to diagnose alopecia. The second tree asks if there is excessive hair growth and if the hair is thick and dark to diagnose hirsutism. The third tree addresses trichotillomania or compulsive hair pulling.