We present a case series (N = 46) of individuals apprehended in Sweden for driving under the influence of drugs (DUID). These cases were selected because the concentrations of amphetamine in blood were abnormally high (> 5.0 mg/L), the highest being 17 mg/L. In comparison, the median blood-amphetamine concentration in a population of DUID offenders (N = 6,613) was 0.70 mg/L. Among the DUID suspects with extremely high blood-amphetamine concentrations there were 38 men (83%) with mean age of 37.8 y (SD 6.8 y) and 8 women (17%) with a mean age of 34.1 y (SD 4.3 y). All had previously been registered in our database (mean 12 times, median 9 times) for drug-related offences, including DUID. The concentration of amphetamine in blood of female offenders was slightly higher than the concentration in male offenders (6.6 mg/L vs. 5.8 mg/L), although this difference was not statistically significant (p > 0.05). The drugs other than amphetamine most frequently encountered in the blood samples were tetrahydrocannabinol and benzodiazepines (diazepam and nordiazepam). The commonest signs of drug use reported by the arresting police officers were bloodshot and glazed (watery) eyes, restlessness, talkativeness, exaggerated reflexes and slurred speech. Unsteady gait and dilated pupils were observed in some but not all individuals. These very high concentrations of amphetamine were tolerated without any fatalities indicating a pronounced adaptation to the pharmacologic effects of this central stimulant. Anecdotal information indicated that those with the very highest concentrations of amphetamine in blood had swallowed the drug to prevent being apprehended in possession of an illicit substance.