Introduction: It has been proposed that chest compression (CC) can provoke recurrent ventricular fibrillation (VF) after defibrillation has restored an organized rhythm (OR). If so this would have major implications for proposed changes in resumption of CC after defibrillation, regardless of rhythm. The aim of this study was to examine our defibrillation data for evidence of post-shock CC-induced VF. Methods: In a defibrillation program using police/fire personnel entire electrocardiograms (ECGs) from defibrillator data cards were examined for initial and post-shock rhythms and CC artifact. Successful shock rhythms were defined as either asystole or OR in the first five seconds post-shock, the latter as at least two QRS complexes during this time period. Artifact from CC was assessed for association with recurrent VF during either asystole or OR. Results: Among 67 patients (pts) defibrillated by police/fire personnel VF recurred at least once in 35 (52%). Entire ECGs were available in 32 of these 35 pts. Chest compression-associated recurrent VF developed in 16 of 32 patients (50%). A total of 78 VF recurrences were observed during the period prior to administration of epinephrine (adrenaline) or other drugs. During post-shock asystole VF recurred 32 times (41% of all recurrent VF episodes); in 19 (59%) VF recurred during CC and in 13 (41%) it was spontaneous. During OR VF recurred 46 times (59% of all recurrent VF episodes); in 36 (78%) VF recurred spontaneously and in only 10 (22%) during CC. Heart rate preceding spontaneous recurrence of VF during OR was 84 ± 35 beats/min, and heart rate preceding CC-associated VF recurrence during OR was 46 ± 20 beats/min (p > 0.001). There was no statistically significant difference in the width of the QRS complex preceding VF recurrence in the CC-associated and spontaneous VF recurrence groups (p = 0.925). Conclusions: VF recurred following successful shocks in 52% of pts. With asystole VF recurred frequently during CC. However, during post-shock OR VF recurred unrelated to CC in most instances. Thus, resumption of CC immediately after shocks that restore an OR is unlikely to provoke recurrent VF, and resumption of CC need not be delayed. © 2005 Elsevier Ireland Ltd. All rights reserved.