In this study, we studied the "passive" diffusion through myoglobin solutions by determining the oxygen diffusion coefficient (DO,) and the oxygen permeability (rho O-2) of metmyoglobin (metMb) solutions (3-33 g . 100 mL(-1)) at 25 degrees C. These oxygen diffusion parameters were determined in a diffusion chamber using a non-steady-state method and were also determined of albumin solutions (4-32 g . 100 mL(-1)) and distilled water for comparison. From these parameters, the oxygen solubility (alpha O-2) could be calculated, because alpha O-2 = rho O-2/DO2. Both DO2 and rho O-2, decreased with increasing metMb and albumin concentration. The values of DO2, rho O-2 and alpha O-2 of both metMb solutions and albumin solutions were comparable with literature values of methemoglobin (metMb) and serum protein solutions. The values of the metMb solutions can be used in following studies of facilitated oxygen diffusion through myoglobin solutions.