The development of numerical analysis and its application to geotechnical problems over the past 20 years have provided geotechnical engineers with an extremely powerful analysis tool. However, the use of such analysis is still not widespread, and when it is used there is all too often evidence of bad practice. Part of the reason for this is a lack of education and of guidance, especially from codes of practice, as to the appropriate use of such methods of analysis. Clearly, some form of initiative is required to promote good practice and allow the full potential of this analysis tool to be realised, both from a safety and an economy perspective. This lecture begins by reviewing the key advantages of numerical analysis over conventional analysis tools, and then debates whether or not it can replace the conventional analysis tools in the design process. Examples from engineering practice are used extensively to illustrate the arguments both for and against the use of numerical analysis.