A 25-year-old national class distance runner came to our clinic complaining of inferior subpatellar pain. After initial diagnostic studies proved inconclusive, the patient was treated conservatively for patellofemoral arthralgia. After allowing him to return to participation following rest and rehabilitation, the patient continued to complain of pain. Further diagnostic studies (bone scan) revealed the presence of a longitudinal stress fracture of the patella. The patient was treated with nonweightbearing exercise and rest. After 8 weeks, he resumed training, and after 20 weeks he was competing on a national class level. This study implicates a patellar stress fracture as a possible etiology in a runner complaining of intractable patellofemoral pain that does not respond to conservative management. J Orthop Sports Phys Ther 1987 9(5):194-197.