The precipitation behavior in an Al-6.8Zn-1.9Mg-1.0Cu-0.12Zr alloy after direct quenching from solutionheat treatment temperature of 470 °C to 205-355 °C was investigated by means of hardness tests, electricalconductivity tests, and transmission electron microscopy. At temperatures below 265 °C, the hardnessincreased gradually to a peak value and then decreased rapidly with time. At 265 °C, the hardness wasalmost unchanged within the initial 2000 s and then decreased gradually. At higher temperatures, the hardnessdecreased slowly with time. The electrical conductivity started to increase after a certain period oftime and then tended to maintain a constant value at all temperatures. Microstructure examination indicatedheterogeneous precipitation of the η phase at grain boundaries and inside grains during holding at205 °C and 325 °C. Based on the electrical conductivity data, the precipitation kinetics could be describedquite well by the Johnson-Mehl-Avrami-Komolgorov relationship with a n value varying between 0.78 and1.33. The activation energy was estimated to be about 44.9 kJ/mol, which is close to that expected for a dislocationdiffusion mechanism. Time-temperature-transformation diagrams were constructed and the nosetemperature ranged from 295 °C to 325 °C.