The microstructure of aluminium alloys based on 380 die-casting alloy was studied in detail, as a function of the alloying elements iron, magnesium, copper and manganese, and the solidification rate. Three methods of solidification were employed to simulate cooling rates obtained from investment, permanent, and die-casting processes, corresponding to similar to 0.4, similar to 12 and similar to 260 degrees C s(-1), respectively, with emphasis on the highest cooling rate. Hardness measurements were carried out on samples obtained from the latter, in the as-cast and T5 tempered conditions (4 h at 25, 155, 180, 200 and 220 degrees C). The results have been discussed and the correlation between the hardness and microstructure as a function of alloying elements is presented. The effect of solution heat treatment on the variations in the microstructure and hardness has also been discussed.