The generally reported observations pertinent to any proposed interpretation of the columnar to equiaxed transition (CET) in as solidified alloys are initially considered. The review then proceeds to consider the proposed mechanisms of equiaxed grain formation, the influence of alloy and processing conditions on the CET, criteria for the termination of columnar growth and, finally, deterministic/stochastic models for predicting the CET. In conclusion, the present level of understanding of the CET and current modelling capabilities are summarised and assessed.