The ability to thermally desorb directly particulate matter, trapped on filter meshes, into the atmospheric pressure chemical ionisation source of a tandem mass spectrometer allowed the simultaneous detection of a range of controlled substances within complex matrices with a high degree of confidence. Dust samples were collected from bundles of banknotes using simple apparatus attached to a portable vacuum cleaner. This technique was employed without additional clean-up procedures, rendering the overall method extremely rapid. The intensities recorded for characteristic gas phase ion transitions allow the determination of the amounts of contaminants present. It has been reported that a significant proportion of bundles of banknotes are contaminated with cocaine. This study found that cocaine and heroin (and two related opiates) were present above the detection threshold on UK banknotes from general circulation. Differences in both the frequency and degree of contamination were apparent between bundles of banknotes from general circulation and those suspected of being associated with the trafficking of drugs. In addition, a significant number of bundles of banknotes, confiscated by H.M. Customs and Excise, were found to be contaminated with detectable levels of tetrahydrocannabinol and 3,4-methylenedioxymethylamphetamine.