Introduction: A growing concern over the use of illicit drugs in the work place has led to an interest in urine analysis as a way to detect drug abuse. Sample adulteration is a serious potential problem in forensic urine drug testing. Federal guidelines define an adulterated specimen as a urine specimen containing a substance that is not a normal constituent or containing an endogenous substance at a concentration that is not a normal physiologic concentration. Adulterants act by either interfering with immunoassay procedures or by converting the target drugs to other compounds. Once the adulterants are converted to other compounds they do not bind to the antibodies used in immunoassay. In some cases these converted compound produce false negative results in confirmatory testing. Adulterants can be classified into two categories. The first category includes in vivo adulteration comprising intentional ingestion of fluids, substances or drugs designed to dilute urine. The second category includes in vitro adulteration such as common household chemicals and nitrite containing agents. Methods of detection of urine adulterants include urine integrity tests, color tests and spectrophotometric methods.