The gas metal arc welding (GMAW) process is highly used in industrial production; therefore great efforts are made to select the appropriate procedure to ensure the highest quality. An area of study directly correlated to the quality of GMAW and widely studied is the control of process stability. The objective of this chapter is to present a bibliographical review of the scientific literature related to qualitative and quantitative indexes to evaluate the stability of the GMAW process. The documents present a compilation of the factors that affect stability, stability indexes, and, finally, a synthesis of the study. With a review of the literature, it was concluded that the highest percentage of investigation was aimed at the study of metal transfer stability, specifically with the short-circuit transfer mode. It is also evident that the main processing techniques to develop the indexes were the mathematical formulation; the statistical analysis; image processing; and monitoring of acoustic signals. In this text, the discussion surrounds the papers, the thesis, and other documents found on the theme.