Today is the last day of work at the United Nations for Hans Blix, the septuagenarian Swedish diplomat who led the team of international inspectors that was searching for biological and chemical weapons in Iraq until the eve of the invasion. With an intense allied search for "weapons of mass destruction" in Iraq still under way, it is too early to reach a final verdict on his legacy. But with each passing day that the allies fail to find any "smoking gun" evidence of terror weapons in Iraq, the carefully calibrated judgments of Mr. Blix and his inspectors are looking ever more credible.

Mr. Blix has taken fire from hawks who believe he should have raised a greater alarm about the danger of Iraqi weapons and from doves who believe he should have suggested more vigorously that Iraq probably had no weapons worth worrying about. In his precise and lawyerly way, Mr. Blix always stuck close to the available evidence. He noted that the Iraqis had acknowledged having biological and chemical weapons and never fully documented their destruction. Some weapons and materials were bombed during the first gulf war and others were dismantled while international inspectors watched after the war. But a residue of uncertainty remained as to whether substantial quantities of forbidden agents or weapons had been squirreled away somewhere.

Iraq raised great suspicion because it repeatedly stonewalled and lied to the first U.N. inspection teams in the 1990's and dragged its heels in dealing with Mr. Blix's follow-up team before the war. No one yet knows what the Iraqis were up to, but lately Mr. Blix has sounded as if he gives some credence to the possibility that Iraq really did destroy virtually all of its weapons and toxic agents, retaining only the ability to start banned programs up again once the world stopped looking.

If the current hunt for terror weapons ultimately hits pay dirt, the discovery will be a warning that even quite intrusive inspections like those by the Blix team are no guarantee of safety. But if the allied search comes up empty, that will suggest that the inspections were successful in containing a potential weapons threat. Mr. Blix and his team will deserve our congratulations.