Objective: To investigate overlap rapid response team (RRT) calls, factors associated with overlap calls, and their impact on RRT call times and patient outcomes. Design and setting: Review of prospectively collected, linked clinical and administrative datasets, at a public adult tertiary hospital during July 2013 to May 2016. Results: There were 11 669 RRT calls to 7223 patients, of which 10 868 calls (93.1%) were to inpatients. The median number of daily calls was 12 (interquartile range [IQR], 9-15 calls; range, 2-29 calls). The median number of daily calls per 1000 hospital admissions was 56.3 (IQR, 41.378.9 calls/1000 admissions; range, 8.3-231.5 calls/1000 admissions), and the median proportion of the day spent at RRT calls was 22.8% (IQR, 16.9%-30.5%). In total, 4575 (39.2%) calls overlapped. Overlap calls, compared with non-overlap calls, had similar patient characteristics, but a longer response time (4 min v 3 min; P < 0.001) and scene time (20 min v 34 min; P < 0.001). The daily number of calls correlated with the number of overnight-stay hospital admissions (r = 0.104; P = 0.001), but not with the total number of hospital admissions (r = 0.035; P = 0.258). The number of overlap calls correlated with the number of RRT calls (r = 0.786; P < 0.001), and also correlated with the proportion of the day spent at RRT calls (r = 0.762; P < 0.001). Overlap calls, compared with non-overlap calls, were more likely to result in an ICU admission (484 calls [11.2%] v 571 calls [8.7%]; P < 0.001). In contrast, efferent limb failure (815 calls [17.8%] v 1195 calls [16.8%]; P = 0.389) and hospital mortality (496 calls [19.3%] v 781 calls [19.6%]; P = 0.823) was similar for overlap and non overlap calls, respectively. Conclusions: Overlap RRT calls are common and influenced by overall RRT and hospital activity. They are more likely to be associated with longer response and scene times and unanticipated ICU admissions.