Assessment of selectivity of Big data sets is generally not straightforward, if at all possible. Some approaches are proposed in this paper. It is argued that the degree to which selectivity – or its assessment – is an issue, depends on the way the data are used for production of statistics. The role Big data can play in that process ranges from minor over supplementary to vital. Methods for inference that are in part or wholly based on Big data need to be developed, with particular attention to their capabilities of dealing with or correcting for selectivity of Big data. This paper elaborates on the current view on these matters at Statistics Netherlands, and concludes with some discussion points for further consideration or research.