Ten participants were included in this double-blind, randomized, crossover study examining the effects of salvinorin A (SA). Participants were administered 0 mg, 8 mg and 12mg of inhaled SA in a counterbalanced way over three sessions that were held consecutively over three days. Subjective and behavioural effects were measured using using a self-reported visual analogue scale (VAS), the Positive and Negative Syndrome Scale (PANSS), the Psychotomimetic States Inventory (PSI), the Clinician Administered Dissociative Symptoms Scale (CADSS), and the Hallucinogen Rating Scale (HRS). Cognitive effects were assessed using using a simple cognitive battery comprised of elements of the WAIS-R. Psychophysiological effects were measured with resting state EEG, blood pressure and heart rate. Plasma cortisol and prolactin levels were also assayed at various time points, as well as SA and salvinorin B levels using a modified liquid-chromatographic-atmospheric pressure chemical ionization-tandem mass spectrometric method. Results reveal that SA produced a wide range of transient, non dose-related effects including dissociative and somaesthetic effects, increased plasma cortisol and prolactin, and reduced resting EEG spectral power, especially for the beta and theta frequencies. SA levels in the blood rapidly increased following its administration. SA did not produce euphoria, cognitive deficits or changes in vital signs.