Beware, there is a 2 in 933 chance of developing a severe skin rash reaction, and the FDA has rejected modafinil for this reason. From Wikipedia:

"The FDA advisory committee voted 12 to 1 against approval, citing concerns about a number of reported cases of skin rash reactions in a trial that included 933 patients on modafinil, including two severe cases which appeared to be "definite" erythema multiforme or Stevens–Johnson syndrome. One of the two severe cases involved hospitalization."