Individualization of pharmacotherapy is essential for rational drug use. Specific, drug information is essential to individualize the pharmacotherapy in order to obtain the optimized pharmacological effect and to avoid serious side effects. Drug information can be divided into two categories ; one is the drug information necessary to select an appropriate drug and to establish a rational dose schedule for each patient, and the other is the information needed to instruct the patient to take medicine correctly. Drug information must be based on the scientific evidence obtained via pharmaceutical analysis and evaluation.