Analysis of heterogeneous polymers, varying in size and substitution pattern, presents a challenge that cannot be met by direct comparisons with a single standard sample. A series of related approaches have been developed to meet this challenge, based on considering the polymers as a population, and applying methods to ascertain degrees of similarity employing first, multivariate analysis, and then two-dimensional correlation spectroscopy formed from their 1-dimensional ¹H NMR spectra. Developments of this approach allow the sensitive detection of structural variation in test samples, the detection of alien materials, as well as identification of both native and aberrant structures with unprecedented sensitivity. The techniques are suitable for any situation in which the quality control of heterogeneous products needs to be analysed, including biosimilar and generic materials as well as other pharmaceutical products.