Tumors and tumor cell lines rapidly consume the amino acid glutamine (Gln) and use it to supply metabolic pathways that support cell growth and proliferation. Much of the research regarding the relationship between glutamine metabolism and cancer is based on the premise that this abundant nutrient represents an important driver of tumor cell anabolism. However, Gln's influence in cell biology and cancer extends far beyond its use as a carbon and nitrogen source for the structural components of dividing cells. Gln is truly a multipurpose nutrient, feeding many additional pathways that boost the ability of cells to communicate with each other and to cope with stress by oncogenic signaling and by the tumor microenvironment. A number of recent reports have highlighted these "non-anabolic" functions of Gln metabolism in regulating cell survival, oxidative stress resistance, signal transduction, and autophagy. Here, we review some of these findings and discuss their relevance to tumor biology and the potential for cancer therapy.