Phospholipid nanosomes are small, uniform liposomes manufactured utilizing supercritical fluid technologies. Supercritical fluids are first used to solvate phospholipid raw materials, and then decompressed to form phospholipid nanosomes that can encapsulate hydrophilic molecules such as proteins and nucleic acids. Hydrophobic therapeutics are co-solvated with phospholipid raw materials in supercritical fluids that, when decompressed, form phospholipid nanosomes encapsulating these drugs in their lipid bilayers. Mathematical modeling and semi-empirical experiments indicate that the size and character of phospholipid nanosomes depend on the several process parameters and material properties including the size and design of decompression nozzle, bubble size, pressure and the rate of decompression, interfacial forces, charge distribution and the nature of compound being encapsulated. Examples are presented for the encapsulation of a protein and hydrophobic drugs. In vitro and in vivo data on breast cancer cells and xenografts in nude mice indicate that paclitaxel nanosomes are less toxic and much more effective than paclitaxel in Cremophor EL (Taxol). Camptothecin nanosomes demonstrate that the normally very water-insoluble camptothecin can be formulated in a biocompatible aqueous medium while retaining in vivo efficacy against lymphoma xenografts in nude mice. In vitro data for betulinic acid nanosomes demonstrate enhanced efficacy against HIV-1 (EC50 of 1.01 microg/ml versus 6.72 microg/ml for neat betulinic acid). Phospholipid nanosomes may find utility in the enhanced delivery of hydrophilic drugs such as recombinant proteins and nucleic acid as well as hydrophobic anticancer and anti-HIV drugs.