The detectionConductivitydetection methods employed in macromolecular separation experiments are examined in detail. After an introductory discussion of general detector characteristics, discussion is divided among physical and chemical detectorsChemical detectors. The former include refractometry, mass sensitive detectorsConcentrationconcentration-sensitive detector, both staticLight scatteringstatic and dynamic light scatteringLight scattering, and viscometryViscometry. The latter encompass various types of mass spectrometryMass spectrometry, and spectroscopic techniques such as absorption, fluorescenceFluorescence, infrared, Raman, and nuclear magneticNuclear magnetic resonance spectroscopy (NMR) resonance. Other, less frequently used techniques such as conductivity, density, and small-angle X-raySmall-angle X-ray scattering (SAXS) scattering are also introduced. The chapter concludes with the determination of chemical heterogeneityChemical heterogeneity in copolymers and how to correct molar mass averages and distributions for the effects of this heterogeneity.