Inclusion Criteria:

1. Male and female outpatients older than 18 and younger than 55 years of age.

2. Subjects with the diagnosis of attention deficit hyperactivity disorder not otherwise specified (ADHD NOS), by Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV), as manifested in clinical evaluation and confirmed by structured interview. This is operationalized by either:

   1. having currently at least 6/9 current items of either inattention or hyperactivity/impulsivity but < 5 items from either list in childhood; or
   2. having 5 out of 9 current DSM-IV items of inattention and/or hyperactivity/impulsivity, but not having 6 current symptoms in either category. This second category will be included independent of the presence or absence of ADHD symptoms in childhood.
3. Subjects will have a current Clinical Global Impression ADHD score of 4 or higher.
4. Subjects with past history of depression or anxiety disorder (including obsessive compulsive disorder [OCD]) without current disorder for > 3 months as ascertained through structured diagnostic interview and clinical exam will be allowed to participate.
5. Subjects treated for anxiety disorders and depression who are on a stable medication regimen for at least three months, and who have a disorder specific CGI-severity score ≤ 3 (mildly ill) and who have a score on the Hamilton-depression and Hamilton-anxiety rating scale below 15 (mild range) will be included in the study.
6. Subjects with past history of substance use disorders but have been asymptomatic for at least 6 months and have a negative drug screen will be allowed to participate.
7. Subjects receiving non-monoamine oxidase inhibitor (MAOI) antidepressants (e.g., selective serotonin reuptake inhibitors [SSRIs], bupropion, venlafaxine), or benzodiazepines who have been on a stable regimen for > 3 months for any of the conditions listed above.
8. Subjects with mild cases of asthma and allergy will be allowed to participate.
9. Subjects with acid reflux syndrome will be allowed to participate.
10. Subjects with hypercholesterolemia who are on a stable dose of cholesterol-lowering medication will be allowed to participate.

Exclusion Criteria:

1. Any clinically unstable psychiatric conditions including the following: acute psychosis, acute panic, acute OCD, acute mania, acute suicidality, lifetime history of bipolar disorder, acute substance use disorders (alcohol or drugs), sociopathy, criminality.
2. Any metabolic, neurological, hepatic, renal, cardiovascular, hematological, ophthalmic, or endocrine disease.

3. Clinically significant abnormal baseline laboratory values which include the following:

   1. Values larger than 20% above the upper range of the laboratory standard of a basic metabolic screen.
   2. Exclusionary blood pressure parameters will include any values above 140 (systolic) and 90 (diastolic).
   3. Exclusionary electrocardiogram (ECG) parameters will include a QTC > 460 msec, QRS > 120 msec, and PR > 200 msec. Subjects having ECG evidence of ischemia or arrhythmia as reviewed by an independent cardiologist.
4. Mental retardation (intelligence quotient [I.Q.] < 75).
5. Organic brain disorders.
6. Pregnant or nursing females.
7. Subjects with current adequate treatment for ADHD or a history of a previous adequate trial of Strattera.
8. Subjects who have failed to respond to an adequate trial, or who have had tolerability problems on Strattera.

9. Only English-speaking subjects will be allowed into the study for the following reasons:

   1. the assessment instruments are not available and have not been adequately standardized in other languages;
   2. the researchers' clinical trials facility is located in Cambridge and not in the Massachusetts General Hospital (MGH) main campus without the availability of translators;
   3. psychiatric questionnaires and evaluations are taxing and adding the complexity of a translator has the potential to make the patient experience even more exhausting.
10. Prior hypersensitivity to Strattera.
11. MAOI antidepressant use currently or within two weeks of starting study.
12. Urinary retention or bladder dysfunction.