This paper presents the analysis of the toxicological investigation of biological samples taken from drivers charged under Section 4 of the Road Traffic Act 1988 for the year 1999. In Scotland, a driver suspected of impairment is taken to the police station where a police surgeon is summoned to examine the driver to ascertain the extent (if any) of impairment. If impairment is suspected through drugs or alcohol, two 10 millilitre blood sam ples are obtained. Polydrug use was detected in 69 per cent (n = 87) of all drug positive blood cases (excluding alcohol). The number of samples submitted to the department of Forensic Medicine and Science from suspected impaired drivers has increased over the years with the highest number received occurring in 1999. Findings were similar to previous years in that polydrug use was prevalent particularly the concurrent use of morphine with Benzodiazepines (88 per cent of all blood morphine positive cases). This combination of drugs has been reported to be the major factor conducive to drug related deaths in the region (4) in the early nineties and remains the favoured cocktail of abuse today. Benzodiazepines remained the most common legal drug detected in impaired drivers. From the levels measured, however, it is more than likely that its use was illicit in the majority of cases. Morphine was the most frequently encountered illegal drug followed by cannabis, which is in contrast to previous years where the latter drug was the most common. Overall, the findings are similar to that of other countries who seem to experience the same trends as Scotland.