Anthracene (ANT) toxicity increases significantly after exposure to simulated or natural sunlight. A simple, rapid method for monitoring the photoinduced short- and long-term toxicity of ANT and other PAHs has been developed. The assay is based on changes in the luminescence intensity and growth rate of Vibrio fischeri. Under suitable conditions, V. fischeri emits a constant amount of light as a metabolic by-product. After exposure to a toxicant, the light intensity can be diminished by an amount which is often proportional to the extent of toxicant impact. Generally, V. fischeri has been used in short-term (15–30 min) assays. However, this does not reveal the toxicity of all hazardous chemicals. In particular, we found ANT is not highly toxic in short-term (e.g. 15 minute) assays. As well, the prevalent phototoxicity of this compound was not revealed in a short-term assay. A long-term (e.g. 18 hour) test was developed that assesses the photoinduced toxicity of ANT.