1 Biochemical Basis of Megaloblastosis.- 2 Diagnosis of Megaloblastic Anemia.- 3 Cobalamin-Folate Interrelations.- 4 The Proteins of Transport of the Cobalamines.- 5 Cobalamin Absorption and Acquired Forms of Cobalamin Malabsorption.- 6 Current Gastroenterologic Aspects of Pernicious Anemia.- 7 Cobalamin Malabsorption in Exocrine Pancreatic Insufficiency in Adults and Children.- 8 Making Sense of Laboratory Tests of Folate Status: Folate Requirements to Sustain Normality.- 9 Prevalence of Folic Acid Deficiency in the French Population.- 10 Effects of some Drugs and Alcohol on Folate and Cobalamin Metabolism.- 11 Neuropsychiatrie Illness and Deficiency of Vitamin B12 and Folate.- 12 Folate Deficiency During Pregnancy and Lactation.- 13 Folic Acid Deficiency in Developing Nations.- 14 Folate Deficiency in Geriatric Patients.- 15 Folate Deficiency in Intensive Care Patients.- 16 Inherited Defects of Folate Metabolism.- 17 The Relationship Between Biopterin and Folate Metabolism.- 18 Inherited Disorders of Colbalamin Metabolism.- 19 Transport of Folate Compounds by Hematopoietic Cells.- 20 Methotrexate and 5-Fluorouracil: Cellular Interactions with Folates.- 21 Methotrexate Pharmacokinetic Studies: Their Clinical Use.