The worker/wrapper transformation is a transformation technique
for improving the performance of programs by changing their types.
Special cases have been used by compiler writers for many years,
but the technique is little known in the wider community, and has
never been described precisely.	 In this talk we show how the
worker/wrapper technique can be explained and formalised in a
simple manner, and considered as a general approach to program
optimisation.  The talk will be aimed at a general audience.