The simultaneous transport of Evans blue dye (EBD) and 125I-labeled canine albumin (IALB) across normal and injured endothelial surface was measured by determining the intimal accumulation of EBD (ME) by a reflectometric method and accumulation of equimolar concentrations of EBD and IALB, ME was related to MI by ME = 0.092 + 5.04 MI - 0.508 MI2 for injured and ME = 0.002 + 0.435 MI (nmol-cm-2) for normal surfaces. Both ME and MI varied nonlinearly with exposure time for injured and linearly with time for normal surfaces, giving apparent permeability coefficients of 0.92 X 10(-8) cm-sec-1 for EBD and 2.00 X 10(-8) cm-sec-1 for albumin. These results show that the transvascular flux of EBD can be related to that of albumin by empirical equations, which is of practical importance but also implies unique underlying physical laws. Study of these physical laws will provide deeper insight into transvascular macromolecular transport processes.