Abstract. We consider data structures and algorithms for preprocessing a labelled list of length n so that, for any given indices i and j we can answer queries of the form: What is the mode or median label in the sequence of labels between indices i and j. Our results are on approximate versions of this problem. Using O( n 1−α ) space, our data structure can find in O(log log 1 α n) time an element whose number of occurrences is at least