This catalog is concerned with the measurement of certain high school outcomes; specifically the progression of students through high school and the way in which students terminate their participation with the secondary education system. The catalog provides a basic inventory of the various methods for estimating high school graduation, completion, and dropout (GCD) rates that are currently being used by federal governmental agencies and state education agencies (SEAs). Following an Introduction, Section 2 provides a brief discussion of the high school processes and outcomes of interest in this catalog. Section 3 describes various types of data systems from which an indicator can be developed. These data systems are represented visually using a contingency table approach that closely resembles the kinds of aggregated, group-level data from which many agencies calculate GCD rates. Section 4 discusses different kinds of "rates" and the way in which data considerations intersect with mathematical formulations to define a statistical indicator. Section 5 offers a brief overview of several of the major sources of data on high school outcomes. These are the sources from which the most prominent, publicly reported findings on high school graduation, completion, and dropout are derived. Section 6 describes the review process used to identify indicators included in the catalog as well as the format of the indicator entries themselves. Finally, Section 7 presents the individual GCD indicator entries. (Contains 11 exhibits.)