Title: Benchmarking Approximate k-Nearest Neighbour Search for Big High Dimensional Dynamic Data. Abstract: Approximate k-Nearest Neighbour (ANN) methods are commonly used for mining information from big high-dimensional datasets. For each application the high-level dataset properties and run-time requirements determine which method will provide the most suitable tradeoffs. However, due to a significant lack of comprehensive benchmarking, judicious method selection is not currently possible for ANN applications that involve frequent online changes to datasets. Here we address this issue by building upon existing benchmarks for static search problems to provide a new benchmarking framework for big high dimensional dynamic data. We apply our framework to dynamic scenarios modelled after common real world applications. In all cases we are able to identify a suitable recall-runtime tradeoff to improve upon a worst-case exhaustive search. Our framework provides a flexible solution to accelerate future ANN research and enable researchers in other online data-rich domains to find suitable methods for handling their ANN searches.