Workplace drug testing is a well‐established application of forensic toxicology and it aims to reduce workplace accidents caused by affected workers. Several classes of abused substances may be involved, such as alcohol, amphetamines, cannabis, cocaine, opiates and also prescription drugs, such as benzodiazepines. The use of alternative biological specimens such as hair, oral fluid or sweat in workplace drug testing presents several advantages over urinalysis—mainly the fact that sample collection can be performed easily without infringing on the examinee's privacy, so the subject is more likely to perform the test. However, drugs are usually present in these alternative specimens at low concentrations and the amount of sample available for analysis is small. The use of highly sensitive techniques is therefore necessary. In fact, the successful interface of liquid chromatography with mass spectrometry (LC‐MS) has brought a new light into bioanalytical and forensic sciences as it allows the detection of drugs and metabolites at concentrations that are difficult to analyse using the more commonly adopted GC‐MS based techniques. This paper will discuss the importance of LC‐MS in supporting workplace drug‐testing programmes. The combination of LC‐MS with innovative instrumentation such as triple quadrupoles, ion traps and time‐of‐flight mass spectrometers will also be focused. Copyright © 2009 John Wiley & Sons, Ltd.