The assay utilizes bioluminescent detection of the ATP level for a rapid screening of apoptosis and cell proliferation simultaneously in mammalian cells. The assay utilizes the enzyme luciferase to catalyze the formation of light from ATP and luciferin. The light can be measured using a luminometer or Beta Counter. The assay can be fully automatic for high throughput (10 seconds/sample) and is highly sensitive (detects 10-100 mammalian cells/well).