Two metal-lux fusions were constructed in Alcaligenes eutrophus by transposon Tn4431 mutagenesis. The resulting strains, named AE1239 (pMOL90::Tn4431) and AE1433 (pMOL30::Tn4431, pMOL28), were respectively emitting light in the presence of copper ions and in the presence of zinc, cadmium, cobalt, and lead ions. Both strains were freeze dried and used as microbial bioluminescent sensors for the evaluation of incinerator fly-ashes (IFA) and soils contaminated by heavy metals. Two detection protocols (with or without direct contact between the bacterial sensors and the IFA) were used to test different batches of IFA that were either not treated or treated in order to be used as recycled material. The bacterial light production measured with a luminometer in the presence of increasing concentrations of IFA was compared with the IFA metal concentration measured by inductively coupled plasma emission spectrometer. The same methodology was used to compare different soils samples from a sandy soil area severely contaminated by heavy metals. Both biosensors could successfully assess the bioavailability of heavy metals. This bioassay appeared to be very simple and rapid since no pretreatment of the samples was required. Those biosensors can either be used to predict the potential risk of the use of heavy metal-recycled materials in the environment or serve as a rapid screening tool for the efficacy of remediation practices used on contaminated soil. © 1996 by John Wiley & Sons, Inc.