The molar enthalpy of formation of the Bi + Cd + Ga + In + Sn + Zn liquid system has been measured at 730 K by direct high-temperature calorimetry. Experimental results are compared with the values calculated using several equations (Kohler, Muggianu, Toop and Hoch-Arpshofen). Finally, an asymmetrical relation (the Toop relation) is proposed to describe the integral molar enthalpy of formation of this 6-component liquid system over the entire composition range.