Institutional term banks (ITBs), such as Inter-Active Terminology for Europe (IATE) in the European Union (EU) institutions and UNTERM in the United Nations, are key sources for the language services of these institutions, and are also used by many other translators and language professionals. These resources are considered authoritative in the translation of institution-specific terminology. However, previous studies have revealed reliability gaps in the content of ITB records, particularly for terms borrowed from specific legal traditions that are used in international legal settings and terms designating singular concepts of national legal systems. This chapter reports further research into the potential causes for such issues and the extent to which terminological records meet institutional translators’ needs. To this end, data were collected through several methods as part of the LETRINT project on legal translation in international institutional settings: (1) interviews with institutional terminologists on the approaches applied to build legal term records for IATE, UNTERM and CuriaTerm (which was initially developed for the needs of the Court of Justice of the EU and later migrated into IATE); (2) an evaluation of ITB relevance and reliability by institutional translators through a survey of 190 respondents; and (3) an assessment of 79 IATE and UNTERM records for 30 terms (of three degrees of legal singularity) from the perspective of translation-oriented legal lexicography. The triangulated results provide evidence of the benefits of applying a systematic legal lexicography approach in the case of CuriaTerm. They also point to significant correlations between translators’ evaluation of IATE and UNTERM for legal translation and the reliability and completeness variations detected in the analysis of illustrative records for each ITB and degree of legal singularity.