The invention provides an assay method for detection and/or quantification of a plurality of nucleic acid or protein targets in a sample. In the method probes are used to associate a detectable tag sequence with each of the selected targets present in the sample. Probes or primers sufficient to identify at least 25, and preferably at least 500, different targets are used. The method involves segregating aliquots of the sample from each other and detecting the tag sequences in each aliquot.