Partial rupture of the flexor hallucis longus tendon in classical ballet dancers, recently well described by Sammarco and Miller, was attributed to rupture of the central fibers of the tendon. Painless triggering or locking of the hallux developed as the tendon glided in its sheath under the medial malleolus. In this report the authors present the case of a patient in whom, in the same tendon, erosive tendinitis was the demonstrated lesion and pain without triggering was the predominant symptom. Since treating this patient, two more ballet dancers have been treated, who were diagnosed as having erosive tendinitis of the flexor hallucis longus tendon, and a third case in a young soccer player has been seen. The only positive physical findings in these patients were tenderness and a minimum amount of crepitation of the medial aspects of the heel, plantar to the sustentaculum tali, which was aggravated by flexion and extension of the interphalangeal joint of the great toe. In all three of these patients complete recovery occurred with minimum conservative efforts.