The load relaxation behaviour of sand-cast alloys ZA8, ZA12, ZA27, Cosmal, SuperCosmal and LM25 were measured at test temperatures of 80, 100 and 120 degreesC. ISO-metric 6 x 1 steel screws were set into cut-threaded sand castings with a preload of 6 kN, and the gradual loss of load was monitored for a period of 10,000 minutes (166.7 hours). The rate of load relaxation increased with temperature, and declined with time. The aluminium alloy LM25 had the best resistance to load relaxation amongst the alloys tested, followed in decreasing order by SuperCosmal, Cosmal and the ZA alloys. All the ZA alloys had very similar resistance to load relaxation, but ZA12 was marginally better and ZA8 marginally poorer than ZA27. Among this group of alloys, with different detailed chemistry, aluminium content appeared to be the most important factor in determining resistance to load relaxation. The kinetics of load relaxation could be described by an expression similar to that obeyed by other zinc alloys in pressure-diecast form: ln P = alpha [Q/RT - ln B - ln t] where P is the load retained after time t at absolute temperature T, alpha and B are constants, Q is an effective activation energy for relaxation and R the gas constant. A systematic variation of the constants alpha and Q showed that the correlation was only approximate.