ILLiad displays the MARC record interface to OCLC records. While many of us know that the title can be found in the 245 field and the ISSN in the 022 field, many of the other fields can be a mystery. What is the difference between the 245 and 246 fields? the 100 and 110 fields? What is the relationship between the 100 and 700 fields? the 490 and 830 fields? What are indicators, subfield codes, and delimiters? In the past year many libraries started cataloging in RDA after more than 30 years of using AACR2. RDA brought changes to the MARC record. This presentation will provide tools to analyze the MARC record in both systems and select the best ones to fill your patrons’ requests.