Primary mouse and rat hepatocyte cultures have long been the gold standard for assessment of cellular changes associated with chemical exposure. While helpful for assessing proliferative and apoptotic responses in vitro, these cultures have limitations due to loss of cells beyond 48hrs incubation. Rat HepatoPac™ was used to extend the culture time beyond 3 days and coupled with downstream quantitative high content imaging (HCI) technology for a more accurate assessment of the cell proliferative response following mitogenic stimulation.