Inclusion Criteria:  are between 21-65 years old Volunteers with no previous medical history (e.g., cardiac or pulmonary disease); are not currently using any type of cannabis have had a previous history with cannabis currently 30 days cannabis free are not taking opioids if female and of a child bearing potential age, are not pregnant or nursing mothers; do not lack sensory/motor deficits that preclude participation in pain-inducing procedures do not have a lifetime history of dependence on cannabis do not have a lifetime history of DSM-IV schizophrenia, bipolar disorder, generalized anxiety or panic disorder, or previous psychosis with or intolerance to cannabinoids Prior THC-containing cannabis experience within the past two years Agrees not to use cannabis outside of the study during participation in the study Agrees not to use opioids or barbiturates during participation in the study Agrees not to drive a motor vehicle within 4 hours following last use of inhaled cannabis during participation in the study  Exclusion Criteria:  Current or past history of cannabis, alcohol or opioid abuse Active pulmonary disease Allergy or past adverse effects or negative past experiences from cannabis Positive urine drug test for THC, barbiturates, opioids, oxycodone, or methadone prior to study session 1 Pregnancy Breastfeeding Prisoner Known cognitive impairment Institutionalized Claustrorphobia MRI contraindications