Bacterial biosensor/-reporters are useful tools for analyzing the bioavailability and/or toxic effects of hydrocarbons. They generally consist of a recombinant organism in which a genetic circuit is placed that serves to produce an easily detectable reporter protein in response to contact with the hydrocarbon. Here we will describe the background of a number of developed biosensor/-reporters and give a few procedures on the types of assays that can be performed with the sensor/reporter cells.