A sliding plate microviscometer for determining the viscosity of asphalt in absolute units is described which utilizes the same constant temperature water baths normally found in control and materials testing laboratories. The instrument is sufficiently accurate and simple to permit bringing the measurement of viscosity in fundamental units into the control laboratory and eventually into asphalt specifications. The sliding plate microviscometer is suitable for routine measurement of viscosity-temperature relationships and viscosity-shear rate dependence. It is compact, rugged, and simple to operate and has a working range of 100 to 100 billion poises. This range permits overlapping with a capillary viscometer in the low viscosity region and allows measurement of the viscosity of the hardest paving grade asphalt at 32 F. Methods for expressing the viscosity-temperature relationship of asphalt are reviewed. Two equations which give straight-line relationships between asphalt viscosity and temperature are discussed. Data obtained with the microviscometer are presented to illustrate these relationships.