This paper describes recent advances in evaluating, quantifying, and propagating various forms of uncertainty in geotechnical earthquake engineering problems. Important developments in the fields of liquefaction engineering, dynamic slope stability, engineering seismology, and lifeline engineering are discussed. The benefits gained through proper treatment of uncertainty include; a well defined measure of the most likely engineering results, a well defined estimate of extreme results, a probability of likelihood ascribed to different realizations, and a mathematical format that lends to performance-based engineering assessment. This paper is by no means comprehensive but highlights some recent studies that contribute to improved probabilistic methodology in the realm of geotechnical earthquake engineering.