The invention provides a method of encapsulating an active substance in an interpolymer complex, to make an encapsulated product in particulate form. The method comprises forming a mixture of a supercritical fluid, an interpolymer complex and an active substance and then causing or allowing the interpolymer complex to encapsulate the active substance. The encapsulated product is then separated from the supercritical fluid and, if necessary, the product is subjected to size reduction to ontain particles in which the active substance is encapsulated by the interpolymer complex.