The present invention is a method for measuring the amount of at least one molecule in a biological sample, the method comprising a) combining the sample, or a derivative thereof, with one or more aptamers and allowing one or more molecules in the sample to bind to the aptamer(s); b) separating bound from unbound molecules; and c) quantifying the molecule(s) bound to the or each aptamer, wherein quantification of the bound molecule(s) is carried out by sequencing at least part of the or each aptamer. Uses of and products derived from the method are also contemplated.