Marjolin's ulcer is an uncommon condition in which malignant transformation occurs in a chronic inflammatory focus. It was originally described in association with a thermal injury, however, its occurrence with protean chronic inflammatory foci has been described. We report the occurrence of and aggressive squamous carcinoma 3 decades after a high voltage electric mark injury to the scalp. This is the first such case described in the literature. The case supportively highlights the role of chronic inflammation and sepsis in epidermal scar cancer development, and it underlines the importance of appropriate wound management initially and expeditious treatment of sepsis and resistant skin ulceration because the malignant behavior of these tumors is aggressive and unpredictable.