Aims: The efficacy of modafinil as a countermeasure in the reduction of cognitive decline following 24 h of sleep deprivation (SD) on subjective sleepiness scales, event-related potential (ERP) P300, and contingent negative variation (CNV) was evaluated. Main methods: Eleven healthy males, age 25-30 years participated. The experiment was performed in five sessions on different days between 7 and 8 a.m. Session 1, baseline recordings; Session 2, after one night's SD; Session 3, 48 h of recovery from SD; Session 4, after 1 week of Session 1, following one night's SD along with modafinil (400 mg/day); Session 5, 48 h of recovery after SD + modafinil. Key findings: Subjective sleepiness scores increased significantly after SD as compared to baseline (P < 0.01), but remained unaltered after modafinil supplementation. There was an increase in N100 and P300 peak latencies of ERP following SD (P < 0.01), which was reduced with modafinil (P < 0.05). There was an increase in CNV M100 and P300 peak latencies after SD (P < 0.01) which decreased with the use of modafinil (P < 0.05). The CNV reaction time increased following SD (P < 0.01) and decreased with the use of modafinil (P < 0.05). No significant effects on ERP N200, P200 latencies and P200, P300 amplitudes and CNV N100, M200 peak latencies and M100, M200 amplitudes were observed. Significance: The results strongly suggest that modafinil in a dose of 400 mg/day, reduces the subjective sleepiness and cognitive decline following 24 h of SD. © 2012 Elsevier Inc.