This study, encompassing 2591 Israeli soldiers, characterized Israeli soldiers with stress fractures to profile individuals who are prone to experience stress fractures: 318 with clinically and scintigraphically proven high grade stress fractures; 237 soldiers with symptoms but with normal scintigraphy; and 2036 soldiers with no symptoms. Soldiers with high grade stress fractures weighed less (68.4 ± 7.9 kg versus 70.5 ± 12.4 kg), smoked less, and reported fewer previous stress fractures, had fewer reports of stress fractures in their family histories, and had fewer incidences of bone diseases than did control subjects. Serum levels of bone specific alkaline phosphatase and osteocalcin were elevated in patients with high grade stress fractures compared with control subjects with no symptoms: 37.6 versus 26.2 units/L, and 10.8 versus 8.8 ng/mL, respectively. Levels of 25-hydroxy vita- min D were lower in patients with high grade stress fractures (25.3 ng/mL) than in control subjects (29.8 ng/mL). This study revealed that several parameters can distinguish soldiers with high grade stress fractures, but their predictive value and precise pathogenetic role remain unclear.