In the recent years many studies have focused on development of rapid, sensitive and cost-efficient bioassays to monitor the toxicity in our environment. E. coli-lux cells emitting bioluminescence (BL) were exposed to various mold extracts and purified mold toxins for acute toxicity prediction. The BL reading after 120 min incubation was taken as a measure of the proportion of living bacterial cells in the reaction mixture and results were plotted in the dose-response curve. Toxic samples killed the bacterial cells dose-dependently. Extracts from 6 species of indoor molds collected from mold-damaged houses showed similar dose-dependency in bacterial viability as in tests where the same extracts were exposed to boar sperm cells and PK-15 porcine kidney epithelial cells and their viability was assessed. Our results suggest that the real-time, multi-sample E. coli-lux assay provides a new method for indoor toxicity assessments.