In Korea medical record administrators/technicians are coding diagnoses and procedures of discharged patients based on their medical records mostly using International Classification of Diseases, 9th revision(ICD-9) and International Classification of Procedures(ICPM) by WHO. This study examined consistency of coding in 63 hospitals in the year of 1992. The statistical data showed great inconsistency in coding patterns among many hospitals. The main reasons of inconsistency were coders errors, ill-defined diagnoses/procedures, no unified route to make new code numbers for the new or ambiguous diagnoses/procedures, inconsistency of selection of using optional(additional) codes, and inconsistency of reference records on coding. Near half of the hospitals do not recheck the accuracy of coding after completion of medical records by physicians. Most of the coders review operation record, admission and discharge record, discharge summary, progress notes, pathology report, and consultation record as references on coding, but 14 hospitals do not review the whole record when they code diagnoses and procedures. Twenty-three hospitals discuss with physicians when they have questions in assigning code numbers. Further study should be done continuously for valid and reliable statistics of diseases and operations and for establishing a systematic unified channel for the new and ambiguous cases.