The records and computer files of 32 patients treated at 1 institution for ossifying fibroma, fibrous dysplasia, osteofibrous dysplasia-like adamantinoma, or adamantinoma of the tibia were reviewed. Nineteen patients had their diagnosis changed, either because of a recurrence or through review of their histology. Six of the 9 patients who had a typical adamantinoma and 6 of the 10 patients who had an osteofibrous dysplasia-like adamantinoma had a diagnosis of 1 of the benign conditions before their adamantinoma was recognized. Only 6 patients actually had osteofibrous dysplasia. Three patients required a resection, but only 1 of the other 3 has been observed > 5 years. This review suggests that many patients with a diagnosis of fibrous dysplasia or osteofibrous dysplasia of the tibia actually have an adamantinoma, and that osteofibrous dysplasia is often a locally aggressive lesion that progresses until it is widely resected. In addition, osteofibrous dysplasia and adamantinoma appear to be related, and osteofibrous dysplasia may be a precursor of adamantinoma.