A screening program was carried out for amino acid disorders in children with mental handicaps from the state of Andhra Pradesh (India) during the last two decades. Forty-one (0.9%) cases were detected with amino acid disorders among 4500 children surveyed. We reported amino acid disorders of rare occurrence such as dicarboxylic aminoaciduria, hydroxykynureninuria, persistent hypertyrosinemia, hydroxyprolinemia, hypervalinemia, etc. A new metabolic defect threoninemia was also detected. We have observed a preponderance of males with amino acid disorders. Parental consanguinity was present in 54% of cases with amino acid disorders.