Minimisation is a method of adaptive stratified sampling that is used in clinical trials, as described by Pocock and Simon.
Normally patients would be allocated to a treatment group randomly and while this maintains a good overall balance, it can lead to imbalances within sub-groups.
For example, if a majority of the patients who were receiving the active drug happened to be male, or smokers, the statistical usefulness of the study would be reduced.
Minimisation addresses this problem by calculating the imbalance within each factor should the patient be allocated to a particular treatment group.
In use, minimisation often maintains a better balance than traditional blocked randomisation, and its advantage rapidly increases with the number of stratification factors.