The relationship between ICPC and ICD-10 is complex. There are some concepts in both which are not exactly represented in the other. However for most rubrics in each classification one or more corresponding rubrics in the other can be mapped.

Because of these complexities, quite often conversion of a code from one classification to the other and then re-conversion back again will not necessarily lead back to the same original code, because in each direction there may be several codes to choose from. Exact choices can only be made if the title of the condition is used with the help of a thesaurus. The point of having the code conversions in this book is only to indicate where the contents of rubrics in each classification overlap.