Ayahuasca, a South American psychotropic plant tea ob- tained from Banisteriopsis caapi and Psychotria viridis, combines monoamine oxidase-inhibiting ß-carboline al- kaloids with N,N-dimethyltryptamine (DMT), a psyche- delic agent showing 5-HT2A agonist activity. In a clinical research setting, ayahuasca has demonstrated a com- bined stimulatory and psychedelic effect profile, as mea- sured by subjective effect self-assessment instruments and dose-dependent changes in spontaneous brain elec- trical activity, which parallel the time course of subjective effects. In the present study, the spatial distribution of ayahuasca-induced changes in brain electrical activity was investigated by means of low-resolution electro- magnetic tomography (LORETA). Electroencephalography recordings were obtained from 18 volunteers after the administration of a dose of encapsulated freeze-dried ayahuasca containing 0.85 mg DMT/kg body weight and placebo. The intracerebral power density distribution was computed with LORETA from spectrally analyzed data, and subjective effects were measured by means of the Hallucinogen Rating Scale (HRS). Statistically signifi- cant differences compared to placebo were observed for LORETA power 60 and 90 min after dosing, together with increases in all six scales of the HRS. Ayahuasca de- creased power density in the alpha-2, delta, theta and beta-1 frequency bands. Power decreases in the delta, alpha-2 and beta-1 bands were found predominantly over the temporo-parieto-occipital junction, whereas theta power was reduced in the temporomedial cortex and in frontomedial regions. The present results suggest the involvement of unimodal and heteromodal associa- tion cortex and limbic structures in the psychological effects elicited by ayahuasca.