There are groups in the community who claim that road safety can be improved if patients who receive benzodiazepine tranquilizers are prevented from driving a car. These groups disregard the fact that there exists no study to show that these drugs are a causal factor in crashes. This paper will mainly review the effect of diazepam which is one of the older compounds. Some studies have shown that performance on psychomotor skill tests are at times affected by diazepam medication. A few of these studies report a decrement in performance, some an improvement, but the results of the vast majority of studies tend to be inconclusive. If detrimental effects occur they usually manifest themselves during the early stages of medication and when high doses are given. Many published studies suffer from methodological errors; there is little evidence that the tests used by the different teams measure the same aspect of behavior. The epidemiological approach has failed to supply the information needed to adequately describe the relationship between all drugs and road safety. Large scale field studies have not been attempted with any pharmaceutical drug. It is difficult to estimate the use of tranquilizers amongst the driving population and to ascertain whether it is similar to that of the general population. Women of middle-age are overrepresented amongst diazepam users and young men are more likely to be involved in a crash.