Comprehensive clinical terminologies such as SNOMED CT tend to overlap with specialized termi-nologies such as LOINC (e.g., for the domain of la-boratory procedures). Terminological systems such as the UMLS are often used to bridge between termi-nologies. However, the integration of LOINC in the UMLS and with other terminologies remains subop-timal. We mapped concepts for laboratory testsfrom LOINC to pre-coordinated SNOMED CT concepts, based on shared relations to other concepts. As LOINC is finer-grained than SNOMED CT, several LOINC codes tend to map to the same SNOMED CT concept. However, a large proportion of LOINC codes could not be mapped to SNOMED CT through this approach, because of underspecified definitions in SNOMED CT and a lack of fine-grained, pre-coordinated concepts in SNOMED CT.