The invention relates to a dendrimer composition in which an effective number of the terminal functionalities are provided with blocking agents, and at least one active substance species is occluded in the dendrimer. A blocking agent is a sufficiently sterically sized compound which readily enters into a chemical bond with a terminal group of a dendrimer but which can also be split off from the dendrimer or can be modified without affecting the chemical structure of the dendrimer and the occluded active substance. The blocking agent can also be provided with a protecting group. The time and duration over which an active substance is released can be controlled. The invention also relates to a process for the preparation of such a composition and to a process for the controlled release of the active substance
