Over the past two decades, the accumulated clinical and research experience has improved our understanding the biology of WHO grade II gliomas (G2G). While there have been relatively few randomized clinical trials in this population, those that exist and the experience from clinical reports have enhanced our understanding of how these tumors progressively increase in size, accumulate additional genetic mutations and ultimately transform into high-grade lesions. Our ability to reliably predict the time sequence of this transformation remains a challenge; however, recent findings have started to clarify selection criteria for adjuvant treatment. G2G remain a fatal disease for many patients. Continued investigation into the biology of these lesions will likely provide the information needed to select more appropriate therapy based on biological and genetic differences in these unique lesions. Some of this information will be derived from the study of high-grade lesions. However, experience has shown that much of the work on high-grade lesions is also applicable to low-grade lesions.