Study Objectives: To evaluate driving performance and psychomotor vigilance in patients with primary insomnia. Design: After 1 night of polysomnography, participants performed a 1-h simulated monotonous driving task and a psychomotor vigilance task (PVT). Self-ratings of sleepiness, mood, and driving performance were completed. Setting: This study was conducted at the CHU of Caen Sleep Unit and the University of Caen. Participants: Twenty-one primary insomnia patients and 16 good sleepers. Interventions: Not applicable. Measurements and Results: Results revealed a larger standard deviation of lateral position (P = 0.023) and more lane crossings (P = 0.03) in insomnia patients than in good sleepers. Analyses of effect of time on task performance showed that the impairment in patients occurred after 20 min of driving, which was not the case for good sleepers. No difference between groups was found for the PVT, neither for the mean reaction time (RT) (P = 0.43) nor the number of lapses (P = 0.21) and the mean slowest 10% 1/RT (P = 0.81). Patients rated their sleepiness level higher (P = 0.06) and their alertness level lower (P = 0.007) than did good sleepers (P = 0.007). The self-evaluation of the driving performance was not different between groups (P = 0.15). Conclusions: These findings revealed that primary insomnia is associated with a performance decrement during a simulated monotonous driving task. We also showed that patients are able to drive safely only for a short time. It appears advisable for clinicians to warn patients about their impaired driving performance that could lead to an increased risk of driving accidents.