Eighteen primary cocaine dependent subjects, enrolled from March 2002 to April 2003, were recruited into an outpatient treatment study in the greater New Haven, Connecticut area. While in this program, they were seen weekly for 45 minute counseling sessions and asked to provide observed urine sam- ples to the clinic three times per week. Enrollment inclusion criteria included: age 18 –55; meeting DSM-IV criteria for cocaine dependence; male or post-menopausal or surgically sterilized female; history of abstinence from benzodiazepines, opioids, barbiturates and amphetamines (confirmed by urine toxicology); and evidence of alcohol abstinence (proven by two negative breathalyzer tests in a fourteen day period). Baseline assessments of physical health included physical examination, psychiatric evaluation, electrocardiogram, urine toxicology for all illicit substances, and blood studies including HIV test.Subjects were excluded if they had: physical signs or labora- tory values suggestive of systemic disorders; abnormal liver function (transaminases greater than three times the upper limit of normal); history of major psychiatric disorders or significant signs of symptoms at the time of screening (schizophrenia,bipolar disorder, or psychosis), use of psychotropic medications within thirty days, history of autoimmune, immunodeficiency, or hypersensitivity disorders, receipt of blood products within three months, other vaccines with thirty days, ongoing infection (in- cluding HIV), any treatment with immunosuppressive (including steroids) or immunostimulant therapy, history of alcohol depen- dence, and current use of any opioid, including methadone.A total of sixty-nine subjects were screened and twenty-two were eligible for treatment. Four subjects entered another study conducted at the center. Subjects failed study entrance due to either meeting one or more exclusion criteria or failure to comply with study guidelines (missed scheduled appointments). Of those enrolled, two subjects did not complete the study due to protocol violations (missed dosing schedule) (Figure 1). For medical safety the assignment to dosage group was not random, instead dosage assignment was escalated. The first ten subjects received four vaccinations at the lower dose (100 g) before the second eight subjects received five vaccinations at the higher dose (400 g).