Introduction- Measurement of diesel smoke in an accurate and consistent manner has been a serious problem for engine and vehicle manufactures@ users@ and agencies charge with enforcing smoke limits. Several instruments@ based on different principles and using different scales@ are in common use. In addition to these@ human observation and judgment are often used to relate smoke to a variety of standards. The purpose of this report is to provide an understanding of the measurement methods can be correlated. Except for defining the various types of smoke@ the report deals solely with the steady-state measurement of black smoke. For the benefit of those who wish to study various aspects of the subject in greater depth@ a list of useful reference is included in the bibliography. This document is divided into the following sections: 1. Definitions and Terminology 2. Procedures for Smoke Evaluation 2.1 Visual 2.2 Photographic 2.3 Instrumental 3. Correlation of Steady-State Smoke Measurements