[11C]Cimbi-36 was recently developed as an agonist radioligand for brain imaging of serotonin 2A receptors (5-HT2A) with positron emission tomography (PET). This may be used to quantify the high-affinity state of 5-HT2A receptors and may have the potential to quantify changes in cerebral 5-HT levels in vivo. We here investigated safety aspects related to clinical use of [11C]Cimbi-36, including radiation dosimetry and in vivo pharmacology.