ABSTRACT Concurrent garbage collectors require write barriers to preserveconsistency, but these barriers impose significant direct and indirect costs. While there has been a lot of work on optimizing write barri-ers, we present the first study of their elision in a concurrent collector. We show conditions under which write barriers are redundant,and describe how these conditions can be applied to both incremental update or snapshot-at-the-beginning barriers. We then evaluatethe potential for write barrier elimination with a trace-based limit study, which shows that a significant percentage of write barriersare redundant. On average, 54 % of incremental barriers and 83 % of snapshot barriers are unnecessary.