A series of mouse lymphoma cell lines of independent origin was investigated with respect to glucocorticoid sensitivity, cellular receptor levels, and properties of receptors. The concentrations of the glucocorticoid dexamethasone required to produce comparable growth-inhibitory effects varied considerably amongst these cell lines. Also a wide range in the number of receptors per cell was found. When the receptor-steroid complexes were compared with respect to nuclear binding properties and affinities for DNA, no differences were seen. For 7 out of 10 cell lines studied we obtained a direct correlation between hormonal sensitivity and the number of cellular receptor sites divided by the dissociation constants KD for the receptor-dexamethasone complexes. This suggests that the receptor is a major quantitative determinant for steroid responsiveness. The limitations of receptor measurements for glucocorticoid therapy of lymphoid neoplastic disease are discussed.