Schizophrenic symptoms and hallucinogenic effects have been thought of as similar for a long time. The aim of this paper is to review the current findings in the research of schizophrenia and hallucinogens; symptoms and effects, brain imaging studies and biochemical studies are compared. Systematic investigations show that the acute symptoms of schizophrenia are particularly similar to the effects of hallucinogens when using psychometric rating scales; APZ, EPI and AMPD, even though dissimilarities have been found. Converging evidence suggests that the acute effects of schizophrenia as well as the effects of hallucinogens act through a common receptor subtype, the 5-HT2A receptor. Brain imaging studies using PET and SPECT indicates that hallucinogenic drugs increase frontal cortical activity, studies have found it to be a result of 5-HT2A receptor stimulation. Interactions between the serotonergic system and other neurotransmitter systems might aid in the understanding of these phenomena.