Objective: Insulin-like growth factor I (IGF-1) has neuroprotective and neurogenerative functions, and is a prognostic factor for cerebral ischemia. We measured serial changes in serum IGF-1 levels in patients resuscitated after cardiopulmonary arrest (CPA) and evaluated the relationship between IGF-1 levels and patient outcomes. Method: Patients who survived for at least 12 hours after return of spontaneous circulation (ROSC) were included in this study. All subjects were at least 15 years old, and none of them had potentially fatal trauma. Serum IGF-1 level was measured immediately after ROSC, and 1, 3, 6, 9 and 12 hours later. We divided the patients into 2 groups: survival group, patients who survived for at least 1 week after ROSC and non-survival group, patients who died within 1 week. Results: There were 16 objective cases; of these, 9 were in the survival group. The IGF-1 levels immediately after ROSC was 98.1±16.9 ng/ml in the survival group and 64.8±9.6 ng/ml in the non-survival group (mean±standard error of mean). Serial changes in IGF-1 levels differed significantly between the 2 groups (P < 0.05). Furthermore, IGF-1 levels were significantly lower in the non-survival group at all measurement time points (P < 0.05). Conclusions: Our preliminary data suggest that IGF-1 levels in patients with ROSC might predict patient outcomes.