Abstract: The present invention relates to an in vitro method for testing the cytotoxicity of a candidate compound for living target cells, said method relying on the detection of the massive release of a cytosolic luminescent enzyme in the supernatant of the cells once they have been voluntarily permeabilized. The detection of this release is rapid and reproducible. More precisely, the method of the invention comprises the steps: a) contacting, with a candidate compound, living target cells that constitutively express in their cytosol a luminescent enzyme, b) isolating the supernatant of the coculture of step a) in a second recipient, c) adding in said second recipient the substrate of said luminescent enzyme, and d) measuring the luminescence emitted in said second recipient. The cytotoxicity of said candidate compound is then proportional to the increase in luminescence measured in step d).