peer reviewed ; Introduction: With growing sophistication of eHealth platforms, the ability increases to share medical information across patients, health care providers, institutions and across borders. This implies more stringent demands on the quality of data-entry at the point-of-care. Non-native English speaking general practitioners experience difficulties in interacting with international classification systems and nomenclatures to facilitate the secondary use of their data and to ensure semantic interoperability. Aim: To identify words and phrases pertaining to the heart failure domain and to explore the difficulties in mapping to corresponding concepts in ICPC-2, ICD-10, SNOMED-CT, and UMLS. Methods: The medical concepts in a Belgian guideline for General Practitioners (GPs) in its French version were extracted manually and coded first in ICPC-2, then ICD-10 by a physician, an expert in classification systems. In addition, mappings were sought with SNOMED-CT and UMLS concepts, using the UMLS SNOMED-CT browser. Results: We retained 143 words and phrases, of which 128 referred to a single concept (1-to-1 mapping), while 15 referred to 2 or more concepts (1-to-n mapping to ICPC rubrics or to the other nomenclatures). In the guideline, words or phrases were often too general for adequate correspondence. Marked discrepancy between semantic tags and types was found. Conclusion: This study illustrates the variability of the various international classifications and nomenclatures, the need for structured guidelines with more attention to precise wording, and the need for classification expertise embedded in sophisticated terminological resources. End-users need support to perform their clinical work in their own language, while still assuring standardized and semantic interoperable medical registration. Collaboration between computational linguists, knowledge engineers, health informaticians and domain experts is needed.