Spontaneous osteonecrosis of the navicular in the adult is known as Mueller-Weiss syndrome, which is a rare disease characterized by a collapse of the lateral portion of the tarsal navicular combined with a medial protrusion of the talar head and peri-navicular osteoarthritis. In this article, we describe a case of spontaneous osteonecrosis of tarsal navicular in a 43-year-old male. Chronic midfoot pain over the dorsomedial aspect of the right foot was resolved after complete removal of the necrotic bone from the tarsal navicular, followed by an autologous bone grafting of the resultant defect. (C) 2011 by the American College of Foot and Ankle Surgeons. All rights reserved.