The recent development of specific methods to measure directly the microrheological determinants of blood fluidity allows to complement or even substitute global measurements of whole blood apparent viscosity or filtrability through sieves containing restricted pores. While such differentiation is mandatory for practical and theoretical reasons, there is the danger of loosing coherence of measurements essential for correlating hemorheology to other sciences. In an attempt to document hemorheological data in a simple yet comprehensive fashion, a test profile for the display of normalized data from subtests on hematocrit, plasma viscosity, red cell "rigidity" and tendency to red cell aggregation is proposed. Using procedures developed in the behavioural sciences, stringend criteria for evaluating the validity, reliability, standardization, economy and usefulness of individual subtests for the blood viscosity determinants and a compounded hemorheology test profile are proposed. There is good evidence that abnormal hemorheological behaviour of red cell plasma mixtures manifest themselves exclusively in situations associated with grossly reduced in vivo driving pressures and thence shear stresses. In these situations, in which a low flow state is caused by general hemodynamic changes, there is a danger that the blood looses its normal fluidity and undergoes a reversible viscidation: We propose the hypothesis that in these situation abnormally blood poses a risk of a flow limitation (and even interruption) by rheological abnormalities described above. The test profile presented has been developed to supply a more valid experimental method for subjecting the above hypothesis to experimental tests in the clinical situation.