This document discusses various causes of oral pigmentation, including physiologic pigmentation, smoking-associated melanosis, oral melanotic macules, café-au-lait macules, pigmented neuroectodermal tumor of infancy, nevomelanocytic lesions, melanoma, amalgam tattoo, drug-induced pigmentation, and heavy metal pigmentation. It provides details on the clinical features, histopathology, etiology, and treatment of each condition.