Cellular senescence is defined as a state of stable cell-cycle arrest that is distinct from quiescence and terminal differentiation. Many stimuli can induce senescence, including telomere shortening and oncogene activation. The phenotypes elicited by pro-senescent signals can be heterogeneous depending on the stimulus and the cell type affected. To date, there is not a definitive marker that can ubiquitously and specifically mark all senescent cells. Therefore, several independent markers must be utilized to ascertain the senescent state of a cell or group of cells. Here, we describe common assays used to assess oncogenic Ras-induced senescence.