Objective: This study evaluated the efficacy and tolerability of modafinil at a range of doses, versus placebo, in alleviating symptoms of ADHD in adults. Method: Adult patients with ADHD were randomized in 1:1:1:1:1 fashion to double-blind treatment with modafinil 255, 340, 425, or 510 mg daily or placebo for 9 weeks. The primary efficacy outcome was the change from baseline at final visit in the Adult ADHD Investigator Symptom Rating Scale (AISRS) total score. Results: A total of 338 patients were enrolled, of whom 330 received at least 1 dose of study medication (modafinil or placebo). No statistically significant difference in the AISRS total score was observed at final visit between any modafinil group and placebo; however, some observations among patients who completed the trial may warrant further investigation. Conclusion: Modafinil was reasonably tolerated but did not demonstrate a benefit on ADHD symptoms in adults. (J. of Att. Dis. 2012; XX(X) 1-XX)