In the large and complex agenda lying between the United States and Mexico, no single item is more difficult and volatile than drugs. Americans periodically rise in outrage at the spectacle of immense quantities of drugs being grown in or shipped through Mexico, often with apparent official protection. Mexicans see a voracious American demand -- 20 million or more users -- overwhelming their resources, inducing the very corruption of which Americans complain and infecting their own people.

Recently, the full array of drug tensions has been on display. In February, a U.S. Drug Enforcement Administration agent was kidnapped and in March found dead in Guadalajara in circumstances suggesting the dereliction of some Mexican police and the complicity of others. The United States, undertaking economic reprisal, brought border traffic to a crawl. The Mexicans were shocked: however tragic, the first death of a DEA agent took place in a "war" that has cost the lives of hundreds of Mexican soldiers and police. But the Mexicans did arrest important police officers and, notably, a major drug trafficker who had fled with evident police aid to Costa Rica. Promises of close cooperation in drug enforcement are now being freely exchanged.

How are we to measure Mexican energy in the eradication of drugs and the pursuit of traffickers and their sometime-official partners in crime? The quantities of crops sprayed or drugs seized and of important dealers and patrons brought to account provide one standard. Another is the readiness of U.S. and Mexican politicians to raise the priority of drug enforcement in official relations. One hears it said in Mexico that a "police issue" should not be allowed to become a foreign policy issue. Why not? Mexican sloth or vigor in this enterprise means more to th American welfare than any nuance of Mexican diplomacy in respect to, say, Nicaragua.

But if the United States is going to rank drug enforcement high on the common agenda, along with immigration, trade and investment, tourism and regional diplomacy, it must become more responsive to Mexico's concerns. That means appreciating the scale of Mexico's own war on drugs -- to which the Mexicans have committed 25,000 troops from their army. It means cooperating on enforcement in ways sensitive to the requirement on Mexican politicians not to be seen being pushed around. And it means a stronger American effort to reduce the phenomenal demand for illegal drugs in this country and meanwhile to enforce American drug laws with no less purpose than we ask of foreign sources and conduits of these hateful substances.