Epileptic seizures during infancy have a wide variety of clinical presentations and the outcome differs according to the etiology. Among the benign and rare causes of infantile seizures, Vitamin B-12 deficiency has been encountered. Common symptoms of Vitamin B-12 deficiency in infants include megaloblastic anemia, feeding difficulties, developmental delay, microcephaly, failure to thrive, hypotonia, lethargy, irritability, involuntary movements, seizures and cerebral atrophy. Involuntary movements and seizures may rarely be the initial symptoms of Vitamin B-12 deficiency. Involuntary movements have also been reported to appear after initiation of Vitamin B-12 supplementation in isolated cases, whereas, no such information exits for seizures. In this paper, three infants with Vitamin B-12 deficiency associated with motor and mental retardation are reported because of tong-Lasting focal/multifocal epileptic seizures following the initiation of intramuscular Vitamin B-12 treatment. Antiepileptics were introduced in addition to Vitamin B-12. Seizures disappeared within a few days or weeks; electroencephalographic findings were normalized in a few months. No relapses occurred during the follow-up period. (c) 2006 Published by Elsevier Ltd on behalf of British Epilepsy Association.