Driving under the influence of drugs is a major problem worldwide. At the moment, several countries have adopted a 'per se' legislation to address this problem. One of the key elements in the enforcement process is the possibility of rapid on-site screening tests to take immediate administrative measures. In this study, the reliability of three oral fluid screening devices (Mavand RapidSTAT, Securetec Drugwipe-5(+), and Dräger DrugTest 5000) was assessed by comparing their on-site results with confirmatory GC-MS plasma analysis. Our results demonstrate that for amphetamine screening, the oral fluid on-site devices on the market today are certainly sensitive enough. RapidSTAT, Drugwipe-5(+), and DrugTest 5000 demonstrated respectively a sensitivity of 93%, 100% and 92% for amphetamine/MDMA. For cocaine screening, sensitivities of 75%, 78% and 67% were obtained for the RapidSTAT, Drugwipe-5(+), and DrugTest 5000 devices, respectively. The studied devices were able to detect about 70% of all cannabis users in a roadside setting. However, a newer version of the DrugTest 5000 test cassette demonstrated a sensitivity of 93%, indicating an increased detection of Delta(9)-tetrahydrocannabinol using 'new generation' oral fluid screening tests with lowered cut-offs. Due to these promising results police officers and judicial experts are keen to use oral fluid screening devices. They believe that their ease of use and diminished amount of false positive results in comparison with urine screening will lead to more roadside tests and more appropriate juridical measures.