The U.S. Supreme Court formulated a two-step test to govern the deference a court should accord an agency interpretation of a statute that it administers. Under this test, if the court determines that "the statute is silent or ambiguous with respect to the specific issue" the court must defer to any reasonable interpretation made by the agency. The author maintains that this doctrine has practical and theoretical defects and proposes a different solution to the problem (now also present in the Italian system too) of the judicial control over the decisions of regulatory agencies. The solution is based on the distinction between primary or "simple" preferences (the preferences that must be considered even when they are not motivated) and secondary preferences (the preferences that are accounted for only if they are conveniently motivated). The courts should retain the competence to make decisions regarding every matter in which simple preferences are involved. They should defer only when the agencies' decisions settle a dispute among secondary preferences. The basic intuition is that agencies are not in a "good position" in order to aggregate people preferences that have a legitimate claim to be considered as such, with no need for justification. It is better that this task continues to be performed by the legislator and by its usual interprets: the courts.