Heating urine samples from high-risk patients for 1 h at 56 degrees C is no longer believed to completely inactivate human immunodeficiency virus (HIV; AIDS virus). To protect staff who are handling infectious samples such as those from drug-addiction units, heating at a higher temperature may be necessary. We report the stability to heat treatment (at 60, 70, and 100 degrees C) at pH 5.1 and 7.6 of some commonly abused drugs, namely, methadone, pethidine, amphetamine, the cocaine metabolite, benzoylecgonine, and the dextropropoxyphene metabolite nordextropropoxyphene. Heat-treating urine at 60 degrees C for 1.5 h or 70 degrees C for 1 h did not significantly affect the measured concentrations of these drugs. However, heat treatment at 100 degrees C for 1 h reduced the recovery of all the drugs. Benzoylecgonine and amphetamine were most susceptible to the different forms of heat treatment.