Background: Higher chest compression release velocity (CCRV) is associated with better outcomes after OHCA. Patient age and gender have been associated with variations in chest wall compliance and compressibility which may impact outcomes. Hypothesis: To evaluate the association between CCRV and OHCA patient age, weight, and gender. Methods: Observational study of prospectively collected OHCA quality improvement data in two suburban EMS agencies in Arizona between 10/1/2008 and 12/31/2016. Patient age and weight were categorized into quartiles for the analysis. CCRV was summarized at each level of the categorical variable by median and inter-quartile range (IQR), and was then compared between different levels by the Kruskal-Wallis test. Results: During the study period, 2,661 OHCA cases were treated. After exclusion criteria, 1,140 cases remained for analysis. Median duration of compressions was 8.70 minutes. Mean CCRV was negatively correlated with age and positively correlated with weight (Table). Male patients exhibited a greater mean CCRV compared to female patients [344.4 mm/s (IQR 307.3-384.6) vs. 331.5 (285.3-385.5), p=0.0133]. Conclusion: Patient characteristics including younger age, male gender, and increased weight were associated with a higher CCRV during OHCA resuscitation.