AbstractTemperature and interparticle spacing measurements are presented for directionally solidified Al–CuAl2and Al–Si eutectic alloys. The results show that care must be taken to ensure that steady state heat flow conditions are established during directional solidification and that the correct definition of spacing is used to obtain interparticle spacing–growth velocity relationships that can be used to assess current eutectic solidification models. The results presented for the Al–Si eutectic show a strong temperature gradient dependence of the spacing–growth velocity relationship which is not predicted by the most recent detailed solidification models.MST/1516