Under the Italian civil law, authentic interpretation is that gi-ven by the legislator himself. According to art. 53 of Act 3.2.1993, n. 29, the parties of a collective agreement may give through a new agreement their interpretation of doubtful clauses. The new agreement is retroactive by provision of law. The paper carnes out the analysis of all the questions concerning authentic interpreta-tion of collective agreements. A particular attention has been paid to authentic interpretation as a tool to settle collective disputes and to the trade unions' powers over employees' rights.