Three grain sizes of expanded perlite were modified with emulsifiers and their potential usefulness in combating oil spills was studied. The tests in the laboratory show that when this perlite is added to a water-oil mixture, the light perlite particles move on the surface spreading over it very quickly (in fractions of a second). It seems that the emulsifier disperses the oil, but at the same time it disperses the perlite particles. At the end there is an emulsion and also perlite particles saturated with it. The usefulness in combating oil spills at sea depends on the following characteristics: (a) With emulsifier-modified perlite some of the oil can be removed (in the form of emulsion), whereas with emulsifiers only this is not possible. Simultaneously the spill is dispersed quickly, before spreading. (b) The action is quick even with a calm sea. Self-mixing is inherent to the process. (c) The action is quick and limited to the surface, where the perlite particles float. There is little waste of the emulsifier in the bulk of the sea. (C) 2002 Elsevier Ltd. All rights reserved.