Background: Vitamin D and C-reactive protein (CRP) have significant effects on brain developmentin numerous psychiatric disorders because of their relationship to inflammatory markers in the clinical course of psychiatric disorders. Aim: To compare the serum levels of vitamin Dand CRP, between the first episode, and chronic disorders of schizophrenia, and methamphetamine-induced psychosis, with a control group. Methods:The study was carried out at AlEman Hospital in Riyadh on 98 subjects classified into: 60 schizophrenic patients, (30 first episodeand 30chronic), 38 patients with methamphetamine-induced psychosis (19 first episode psychosis and 19 chronic) and comparing them with 20 normal healthy subjects according to serum levels of vitamin Dand CRP. Results:There was a significant decrease in vitamin Din each of schizophrenia,and methamphetamine-induced psychosis drug in chronicpatients compared with first episode.However, CRP showed significant increase in each of schizophrenia, andmethamphetamine-induced psychosis in chronic patients compared with first episode. Conclusion: Chronic patients had much lower vitamin D levels than patients who had experienced a first episode, and their CRP levels were also significantly higher. Keywords: schizophrenia, methamphetamine, vitamin D, CRP.