This report describes the experience of the Southeastern Cancer Study Group (SECSG) with a transport medium used for immunologic phenotyping of non-Hodgkin’s lymphomas. In a 2-mo pilot study, portions of 53 specimens of non-Hodgkin's lymphoma from four member institutions of the SECSG and affiliated community hospitals were sent by regular mail to a central laboratory. Immunologic phenotyping was carried out using a frozen section immunoperoxidase technique. In 48 of the cases, a clear-cut immunologic phenotype was obtained. Thirty-four tumors were of B cell origin and 7 had T cell markers. Six of the remaining lymphomas had neither B nor T cell markers, and the seventh had both. In 12 cases, phenotyping was also carried out at the originating institution using conventional cell suspension techniques; agreement between the two methods was excellent. The immunologic results were correlated with histopathologic diagnosis standardized using the Working Formulation for non-Hodgkin’s lymphomas. It was found that the low grade tumors were all B cell, but that the intermediate grade tumors were very heterogeneous immunologically. About one-fourth of the diffuse, intermediate grade or miscellaneous tumors had T cell markers. Our results indicate that immunologic phenotyping may be performed satisfactorily on transported material, making multiinstitution studies on the prognostic significance of immunologic phenotype in non- Hodgkin’s lymphomas feasible.