This contribution discusses basic problems and fundamental requirements for a universally applicable, unified and metrologically correct calibration of differential scanning calorimeters (DSC). The essential features of previously published recommendations of the German Society for Thermal Analysis (GEFTA) [see Hohne et al., Thermochim. Acta 160 (1990) 112; Cammenga et al., Thermochim. Acta 219 (1993) 333-343; Sarge et al., Thermochim. Acta 247 (1994) 129-168; J. Thermal Anal. 49 (1997) 1125-1134] developed for a correct and instrument-independent calibration of temperature, heat and heat flow rate of DSC, are outlined.