It is shown that differential scanning calorimetry may be used to determine miscibility gaps in micromolecular as well as in macromolecular systems. The first deviation of the signal from the base line is indicative of the onset of liquid-liquid phase separation and allows determination of the cloud-point curve. The area of the endo- or exothermic signal is related to the heat of demixing and may be analysed to supply information about the enthalpic part of the pair-interaction parameter. The method is tested on the systems water/nicotine and n-butanol/poly(methyl methacrylate).