A technique for isolation of HIV using selective cultures of T4 cells obtained from peripheral blood by immunochemical separation was developed and optimized. Using this method infectious virus could be isolated in single isolation attempts from 89% of 35 HIV-infected patients in different stages of immunodeficiency. This isolation frequency was virtually independent of the stage of the disease, in contrast to the results obtained by the conventional isolation technique based on peripheral mononuclear cells (PMC). It is concluded that isolation of HIV from selected T4 cells is superior to other methods when isolation is attempted from healthy HIV-infected individuals.