We have developed a direct toxicity assay for soils, sediments and sludges that is specific for heavy‐metal toxicity. In the assay, a β‐galactosidase‐producingstrain of Escherichia coll is mixed with the solids sample together with a small volume (1.0 ml/0.5 to 1.0 g of solids) of eluent Extraction of metals from the solids sample is not required. Controls run with the assay eliminate interference due to indigenous β‐ga‐lactosidase activity or interaction between the solid matrix and the chromaphore. Use of 0.1 M sodium nitrate as eluent was found to yield somewhat higher sensitivity to heavy metals in solid‐phase samples than MilliQ water. Application of the assay to a diverse array of soils, sludges, and sediments indicated that samples from industrial sites were generally more toxic than those from residential or commercial sites. Heavy‐metal toxicity was correlated with the copper and zinc content of solids samples, but toxicity varied considerably at the lower range of metal contents. The proposed solid‐phase assay should prove useful as a screening test for heavy‐metal toxicity in soils, sediments, and sludges. It can also help distinguish between heavy metals and organic chemicals as the cause of toxicity in solid‐phase samples.