This is an open-label (name of assigned treatment is known), single-center study of the pharmacokinetics (blood levels) and safety of 3 single doses of methylphenidate HCl administered orally (by mouth) to healthy Japanese adult male volunteers. Methylphenidate HCl is a drug that is currently approved for the treatment of adults with attention-deficit/hyperactivity disorder (ADHD) in regions outside Japan, including the United States where this study will be conducted. Volunteers will participate in the study for a maximum of 42 days. Blood samples will be collected from volunteers during the study to determine the concentration of the methylphenidate HCl in the blood after dosing. Safety will be monitored throughout the study by evaluating adverse events reported, changes in clinical laboratory test results, vital signs measurements, physical examination results, and other protocol-specified safety assessments. All volunteers will receive a single oral dose of methylphenidate HCl with 240 mL (1 cup) of noncarbonated water after at least a 10-hour fast (without eating food) during 3 treatment periods as follows: Period 1, one 36-mg tablet; Period 2, three 18-mg tablets; and Period 3, two 36-mg tablets. Treatment periods will be separated by 3 to 7 days. Volunteers will continue fasting until at least 4 hours after dosing.