This symposium was conceived two years ago as a result of a feeling by ASTM Committee D-4 on Road and Paving Materials that there was a need for a greater appreciation for and use of statistics by those responsible for the development and standardization of test methods for bituminous materials; and furthermore, that there was a real need for a better understanding of the practical significance of many of the test methods. I was particularly in sympathy with this attitude since I had recently attempted to secure acceptance of “statements of precision” for nine different tests on asphalt emulsions. I encountered considerable and, occasionally, heated divergence of opinion as to just how precision should be measured and expressed and even as to what practical significance could be attributed to any test result. Certainly no one can deny that, as a whole, tests on bituminous materials tend to be (a) largely empirical, (b) of dubious precision as far as engineering uses are concerned, and (c) only vaguely correlated with actual field performance of pavements. This is, of course, attributable to the historical background of paving technology. Most of the tests were designed originally to define the source rather than the nature of the material. With the years there has been an increasing tendency to transpose certain source-defining tests to performance-defining tests without any particular attempt at field correlation. Furthermore, levels of test precision which were entirely adequate for defining source may or may not be adequate when performance must be defined, as in writing so-called “quality” specifications. Even in the few cases in which test methods have been correlated with performance and engineering requirements, modern statistical concepts raise serious doubts about the validity of both the experiment design and interpretation of results. The testing of bituminous materials has not kept pace with testing of other materials of construction, for example, metals and plastics, both as to the level of precision attained and the degree to which properties of engineering significance are being measured. Continued full utilization of inexpensive and versatile bituminous materials in an atomic-age technology requires an up-to-date, precise description of their properties and capabilities.