We describe a standard set of quantity names and symbols related to the estimation of kinetic parameters from dynamic contrast‐enhanced T₁‐weighted magnetic resonance imaging data, using diffusable agents such as gadopentetate dimeglumine (Gd‐DTPA). These include a) the volume transfer constant K^trans (min⁻¹); b) the volume of extravascular extracellular space (EES) per unit volume of tissue v_e (0 < v_e < 1); and c) the flux rate constant between EES and plasma k_ep (min⁻¹). The rate constant is the ratio of the transfer constant to the EES (k_ep = K^trans/v_e). Under flow‐limited conditions K^trans equals the blood plasma flow per unit volume of tissue; under permeability‐limited conditions K^trans equals the permeability surface area product per unit volume of tissue. We relate these quantities to previously published work from our groups; our future publications will refer to these standardized terms, and we propose that these be adopted as international standards. J. Magn. Reson. Imaging 10:223–232, 1999. © 1999 Wiley‐Liss, Inc.