Applications of isoelectric focusing (IEF) in soil science are illustrated. The materials studied, i. e. humic substances and organic fertilisers, and their behaviour when subjected to IEF are briefly described. Preliminary studies carried out on soil indicate a relation between the isoelectric point and molecular weight, and a connection with humification has been hypothesised; therefore, assessment of soil conditions could be an application of IEF. Another application is evaluation of the stabilisation of organic fertilisers. Finally, IEF can be used to distinguish different organic matrices, as such and in mixtures with mineral fertilisers.