PURPOSE:This article describes a previously unreported fifth metacarpal stress fracture. CASE SUMMARY:A female softball pitcher presented with gradual development of dorsal pain in her pitching hand. A radioisotope scan showed increased uptake in the fifth metacarpal. This supported a clinical diagnosis of a stress fracture, and the patient was treated with a period of relative rest. At 6 weeks, the patient was able to return to pitching with technique modification. DISCUSSION:Seven cases of metacarpal stress fractures have been reported, yet none involved the fifth metacarpal. The causes of a fifth metacarpal stress fracture differ from those of other metacarpals and may be a combination of extrinsic forces from the ball and intrinsic forces from muscle pull. Although treatment involves the standard rest period, technique must be assessed and appropriately adjusted. RELEVANCE:Metacarpal stress fractures should be considered in athletes with persistent hand pain where repetitive grip function is used.