A simple conceptual model of blood flow in the microcirculation, including small arteries, arterioles, capillaries, venules, and small veins, with linearized equations of motion and simplifying assumptions. The pulsatility of the imposed blood pressure and the importance of the inertial terms are expressed by the Wormersley frequency parameter alpha. In large arteries, alpha is greater than 1. For microvessels, alpha is near zero, viscous forces predominate, and the pressure gradient is balanced by shear. Using transmission line nomenclature, with large alpha, the wave propagation equation results. When viscous forces dominate, the diffusion equation results, and pulsatile flow is highly attenuated and dispersive. Decrease in the pressure amplitude and change in the wave form are characteristic. The numerical values obtained are in qualitative agreement with experimental measurements. The model is being extended to include nonNewtonian effects and tissue compliance. 24 pp. Ref.