This study assessed the effect of intravenous alcohol infusions on psychomotor impairment and compared it with that of alcohol administered orally. Comparisons were made between three European drink-driving limits of blood alcohol concentration (BAC) (20, 50 and 80 mg 100 ml-1) and an oral dose of alcohol 0.75 mg kg-1. Twelve volunteers, aged 22-34 yr, were recruited. At targets of 20, 50 and and 80 mg 100 ml-1, the mean (SD) BAC was 22.1 (3.7), 51.5 (3.3) and 80.5 (4.2) mg 100 ml-1, respectively. The peak BAC following an oral dose of alcohol 0.75 mg kg-1 ranged from 19 to 68 mg 100 ml-1. In psychomotor testing, choice reaction time deteriorated with increasing BAC and showed significant differences between baseline and the 50 (P < 0.05) and 80 mg 100 ml-1 (P < 0.01) conditions. Dual-task secondary reaction time deteriorated with increasing BAC and showed a statistically significant difference between all groups and baseline (oral and 20 mg groups, P < 0.05; 50 and 80 mg groups, P < 0.01). Dual-task tracking in the 50 and 80 mg groups was significantly different from baseline (P < 0.05 and P < 0.01, respectively). Oral dosing resulted in widely variable BACs, making it difficult to assess psychomotor impairment reliably. An intravenous infusion enables the BAC to be maintained within a narrow range. This allows precision when investigating the effects of alcohol on psychomotor performance.