A total of 120 subjects will be recruited in the study. Subjects will be eligible to participate if they:

1. Are at least 18 years of age;
2. Smoked more than10 cigarettes/day for the past one year;
3. Willing to make a quit attempt;
4. Able to participate fully in all aspects of the study; and
5. Have been provided with, understand, and have signed the informed consent.

Individuals will be excluded from study participation if they:

1. Meet diagnostic criteria for current major depressive disorder or lifetime history of bipolar disorder or schizophrenia. Patients with mild or moderate depressive symptoms [Beck Depression Inventory, Second Edition ≤ 28], but who do not meet current diagnostic criteria for major depressive disorder, will be included;
2. Are currently (within past 30 days) using antipsychotics or antidepressants;
3. Are currently (in previous 30 days) using any treatments for tobacco dependence (i.e., behavioral therapy, nicotine replacement therapy, bupropion SR, clonidine, or nortriptyline);
4. Have used an investigational drug within the 30 days prior to enrolling in this study;
5. Have ever used an herbal product for tobacco cessation;
6. Have recent history (in the past 3 months) of alcohol abuse or dependence as assessed by the CAGE questionnaire and study investigators;
7. Have a recent history of drug abuse as assessed by the Drug Abuse Screening Test 20 (DAST-20) and physician interview;
8. Are pregnant, lactating, or of child bearing potential, likely to become pregnant during the medication phase and not willing to use a reliable form of contraception. Reliable forms of contraception include barrier (diaphragm or condom with spermicidal jelly), injections, intrauterine device [IUD], surgical sterilization and abstinence;
9. Have a history of any major cardiovascular events in the past 6 months including unstable angina, acute MI or coronary angioplasty;
10. Have clinically significant acute or chronic progressive or unstable neurologic, hepatic, renal, cardiovascular, respiratory or metabolic disease;
11. Are currently on medications interacting with St. John?s Wort including warfarin, antiretrovirals (particularly indinavir and nevirapine), cyclosporine and tacrolimus, digoxin, nifedipine and verapamil, theophylline, all serotonergic drugs (serotonin reuptake inhibitors, tricyclic antidepressants, tramadol, venlafaxine, tryptophan and buspirone), MAO inhibitors, oral contraceptives, anti-cancer agents including imatinib and irinotecan, migraine medications (sumatriptan and zolmitriptan), methadone, lithium, sibutramine, atorvastatin and simvastatin, midazolam, alprazolam, fexofenadine, omeprazole, and general anesthetics (fentanyl, propofol, and sevoflurane);
12. Have another household member or relative participating in the study;
13. Have a known allergy to St. John?s Wort;
14. Have a history of photosensitivity;
15. Are professional drivers or operators of heavy machinery; and
16. Are scheduled for a planned surgical procedure within five days of taking SJW.