Considerable efforts have been made during the past two decades to investigate gas injection operations in steelmaking ladles. Towards these, numerous physical and mathematical model studies embodying aqueous as well as full scale systems have been reported. On the basis of an extensive literature search, a summary, discussion and analysis of these are now presented. For the sake of convenience and clarity of presentation, studies have been categorised into three major groups: (1) physical modelling studies, (2) combined physical and mathematical modelling studies and (3) mathematical modelling studies. In each of these categories, a great number of publications on various phenomena, such as gas-liquid interactions, turbulent fluid flow, mixing, solid-liquid mass transfer, etc. have been reported. Accordingly, and as discussed in the text, considerable improvements have resulted in our understanding of the various gas injection induced phenomena in ladle metallurgy operations. Coupled with these, extensive mathematical modelling studies have also lead to a reasonably accurate framework for carrying out engineering design and process calculations. Nonetheless, some obscurities and uncertainties still remain and these are pointed out, together with those areas where further work is needed.