During brain development, cell death is a physiological process which allows the elimination of cells produced in excess. During adulthood, when there is no or little physiologic cell death, an increase in cell loss is usually caused by neurologic disorders or by exposure to neurotoxic chemicals. Measurements of cell death are often used a first line of investigation on chemicals. Cell death in neuronal or glial cultures in vitro can be quantified with a variety of assays based on different properties of live and dead cells. Thus, healthy cells exclude dye (e.g., trypan blue, propidium iodide) or possess metabolic activity to cause a compound's conversion to a colored or fluorescent one (e.g., MTT, calcein AM) while dead cells do not. Conversely, dying cells release enzymes in the medium (e.g., LDH) whose quantification is proportional to the number of dead cells. This chapter describes several relatively rapid, inexpensive and reliable methods for measuring cell death and in neurons and astrocytes in primary cultures or in neuronal and glial cell lines.