Clandestine production accounts for almost all methamphetamine trafficked and abused in the United States. Illicit methamphetamine manufacture can be accomplished in a variety of ways, but the drug is most commonly produced using the ephedrine/pseudoephedrine reduction method. During the past 2 years, several bulk ephedrine seizures destined for Mexico have focused attention on the magnitude of ephedrine acquisition by organized crime drug groups operating from Mexico and in the United States and have set in motion an effort to focus international attention on the ephedrine diversion problem. Drug law enforcement efforts against clandestine methamphetamine producers constitute a "cat and mouse" game between efforts to cut off chemical supplies and efforts to obtain them from non-regulated sources. Domestically, large-scale production of methamphetamine is centered in California. In addition, methamphetamine is increasingly being produced in Mexico and then smuggled into the United States. Although methamphetamine suppliers throughout the United States have traditionally been outlaw motorcycle gangs and numerous other independent trafficking groups, organized crime drug groups operating from Mexico currently dominate methamphetamine trafficking in the United States. Chemical diversion initiatives are described, and major methamphetamine trafficking organizations and regional methamphetamine trafficking trends are noted. Data on methamphetamine seizures and purchases are appended. 12 tables and 3 figures