Die-to-database inspection allows a repetitive or non-repetitive pattern of any scale to be examined for data errors, random defects, and repetitive defects. This type of inspection finds repetitive defects that would not be detected in a die-to-die inspection mode. Increasing circuit and process complexity requires more intricate methods of data handling in terms of layout, sizing, and merging from design to final pattern generation. This increase in complexity of both data and data manipulation enhances the probability that an inadvertent data change may occur at some point between layout and final product. Inspection of the mask or reticle to the verified design will either find these unwanted changes or verify that no changes have occurred. Use of the Calma database as the source for the inspection provides a separate data conversion path parallel to the path used for pattern generation. This allows a more extensive data verification to be performed. If an intermediate format such as Electromask, Mann, or Mebes is used as source, some types of errors would not be detected since the data used for pattern generation and inspection would be one and the same. Thus, both the final product and the methods of data manipulation needed to produce the final product are checked when the Calma database is used as the inspection source. Pattern defects found with this type of inspection will be presented and explained as to their cause. The factors and limitations inherent to pure database inspection using the KLA-221 Klaris inspection system will be discussed.