Define the frequency and survival pattern of cardiac arrests in relation to the hospital day of event and etiology of arrest.Retrospective cohort study of adult in-hospital cardiac arrests between July 1, 2005, and June 30, 2013, that were classified by etiology of deterioration. Arrests were divided based on hospital day (HD) of event (HD1, HD2-7, HD>7 days), and analysis of frequency was performed. The primary outcome of survival to discharge and secondary outcomes of return of spontaneous circulation (ROSC) and favorable neurological outcomes were compared using multivariable logistic regression analysis.A total of 627 cases were included, 193 (30.8%) cases in group HD1, 206 (32.9%) in HD2-7, and 228 (36.4%) in HD>7. Etiology of arrest demonstrated variability across the groups (p<0.001). Arrests due to ventilation issues increased in frequency with longer hospitalization (p<0.001) while arrests due to dysrhythmia had the opposite trend (p=0.014). Rates of survival to discharge (p=0.038) and favorable neurological outcomes (p=0.002) were lower with increasing hospital days while ROSC was not different among the groups (p=0.183). Survival was highest for HD1 (HD1: 38.9% [95% CI, 32.0-45.7%], p=0.002 vs HD2-7: 34.0% [95% CI, 27.5-40.4%], p<0.001 vs HD>7: 27.2% [95% CI, 21.4-33.0%], p<0.001).The etiology of cardiac arrests varies in frequency as length of hospitalization increases. Survival rates and favorable neurological outcomes are lower for in-hospital arrests occurring later in the hospitalization, even when adjusted for age, sex, and location of event. Understanding these issues may help with focusing therapies and accurate prognostication.