The following are claimed: (A) foam comprising (a) a matrix comprising an organic thermoplastic polymer and (b) continuous, open-cell pores dispersed in the matrix. The foam is produced by (1) combining an organic polymer with a fugitive compsn. that is a solid crystalline material which melts at above 25C. (2) solidifying the isotropic soln. to produce a foam precursor contg. crystals of the fugitive compsn.; and (3) removing crystals of fugitive compsn. from the foam precursor to give a continuous, open-cell foam., (B) medicated foam for topical admin. comprising (a) a matrix of an organic polymer and (b) continuous open-cell pores dispersed in the matrix. The cells are at least partially filled with a medicament, and are sized so that the medicament is released from the foam at a controlled rate of dosage to a patient. The foam is produced by (1) combining an organic polymer with a fugitive comspn. (as described above; (2) co-melting and co-dissolving the compsn. throughout the polymer to give a substantially isotropic soln.; (3) solidifying the soln. to give a foam precursor contg. crystals of the fugitive compsn.; (4) removing the fugitive cpd. from the foam precursor to produce a continuous, open-cell foam; and (5) adding a medicament to the foam to at least partially filled cell so the foam. (C) Foam comprising an organic polymeric matrix in which continuous open-cell pores are dispersed. The pores contain living cells, the foam is prepd. by (1) combining an organic polymer with a fugitive compsn. (as described above); (2) co-melting and co-dissolving the fugitive compsn. with the polymer, to produce an isotropic soln.; (3) solidifying the isotropic soln. to produce a foam precursor contg. crystals of the fugitive compsn. (4) removing the crystals of the fugitive compsn. from the foam precursor to give a continuous, open-cell foam; and (5) adding selected living cells to the foam for inhabiting the pores.    USE -   The foams may be used, e.g. in drug delivery systems, constructs for bone, cartilage or organ regeneration, filters for protein fractionation, matrices for gas and fluid filtration, templates for three-dimensional cell cultures, bioreactor substrate material constructs contg. immobilised chemical and biological reagents, etc..    ADVANTAGE -   The foams may be produced on large scales without the need for new equipment. They may be prepd. by processes which allow control of pore size, chemical reactivity and mechanical properties.