Objectives: Delayed and nonunion of the tibia are not uncommon in orthopaedic practice. Multiple methods of treatment have been developed with variable results. The objective of this study was to define disease-specific and treatment-related factors of prognostic significance in patients undergoing shock wave therapy for tibia nonunion. Design: Retrospective analysis. Patients: One hundred ninety-two patients treated with extracorporeal shock wave therapy (ESWT) at a single referral trauma center, AUVA-Trauma Center Meidling, a large single-referral trauma center located in Vienna, Austria, in an attempt to determine the feasibility and factors associated with the use of ESWT in the treatment for tibia nonunion. Intervention: ESWT coupled with posttreatment immobilization, external fixation, or ESWT alone. Main Outcome Measures: Fracture healing, overall healing percent, and factors associated with ESWT success or failure. Results: At the time of last follow up, 138 of 172 (80.2%) patients have demonstrated complete fracture healing. Mean time from first shock wave therapy to complete healing of the tibia nonunion was 4.8 ± 4.0 months. Number of orthopaedic operations (P = 0.003), shock wave treatments (P = 0.002), and pulses delivered (P = 0.04) were significantly associated with complete bone healing. Patients requiring multiple (more than one) shock wave treatments versus a single treatment had a significantly lower likelihood of fracture healing (P = 0.003). This may be attributable to the finding that a significantly greater proportion of patients with multiple rather than single ESWT treatments had three or more prior orthopaedic procedures (more than one ESWT, 63.9% versus one ESWT, 23.5%; P < 0.001). Conclusions: ESWT is a feasible treatment modality for tibia nonunion.