Objective:To assess the frequency of neuropsychiatric and neurological problems in apparently healthy young vegetarians and estimate serum Vitamin B12, methylmalonic acid (MMA), and folic acid levels.Methods:This prospective study was conducted in the Department of Biochemistry, Basic Medical Sciences Institute (BMSI), Jinnah Postgraduate Medical Center (JPMC), Karachi, Pakistan, in the years of 2012 and 2013. The data of 100 vegetarians and 100 omnivores were analyzed and compared.Results:The serum concentration of Vitamin B12 was significantly lower in the vegetarian group compared with the omnivore group (238±71 pg/ml vs. 401±170 pg/ml, p<0.001). In the vegetarian group, MMA level was significantly higher compared with the omnivores (285±89.4 nmol/L vs. 191±40.5 nmol/L, p<0.001). Regarding the neuropsychiatric and neurologic problems in the vegetarian group, the frequency of depression was 31% compared with 12% in the omnivore (p=0.002), paresthesias were 11% compared with 3% in the omnivores (p=0.04), peripheral neuropathy was 9% compared with 2% in the omnivores (p=0.05), psychosis was found in 11% subjects compared with 3% in the omnivores (p=0.04).Conclusion:Vegetarians have Vitamin B12 deficiency and are more prone to developing neuropsychiatric and neurological problems.