A pure dose of the hallucinogenic drug LSD is so small that it must be sold to retail customers in a "carrier" created by dissolving pure LSD and, inter alia, spraying the resulting solution on paper. That paper is then cut into "one-dose" squares, which users swallow, lick, or drop into a beverage to release the drug. Petitioners were convicted in the District Court of selling 10 sheets (1,000 doses) of blotter paper containing LSD, in violation of 21 U.S.C. 841(a). Section 841(b)(1)(B) calls for a 5-year mandatory minimum sentence for the offense of distributing more than one gram of "a mixture or substance containing a detectable amount" of LSD. Although petitioners pure LSD weighed only 50 milligrams, the court included the total weight of the paper and LSD, 5.7 grams, in calculating their sentences, thus requiring the imposition of the mandatory minimum sentence. The 5.7 grams was also used to determine the base offense level under the United States Sentencing Commission Guidelines Manual (Sentencing Guidelines). The Court of Appeals affirmed, rejecting petitioners arguments that the carrier mediums weight should not be included for sentencing purposes, and, alternatively, that construing the statute and the Sentencing Guidelines to require the carrier mediums inclusion would violate the right to equal protection incorporated in the Due Process Clause of the Fifth Amendment.

Held:

1. The statute requires the weight of the carrier medium to be included when determining the appropriate sentencing for trafficking in LSD. Pp. 456-464.

(a) Since the statute refers to a "mixture or substance containing a detectable amount," the entire mixture or substance is to be weighed when calculating the sentence. This reading is supported by the history of Congress attempts to control illegal drug distribution, and by the statutes structure. Congress knew how to indicate that the weight of a pure drug was to be used to determine a sentence, having done so with respect to phencyclidine (PCP) and methamphetamine by providing for a mandatory minimum sentence based either on the weight of the mixture or substance containing a detectable amount of the drugs, or on lower weights of the pure drugs. And Congress clearly intended the dilutant, [500 U.S. 453, 454] cutting agent, or carrier medium of heroin and cocaine to be included in those drugs weight for sentencing purposes. Pp. 456-461.

(b) The blotter paper used here, and blotter paper customarily used to distribute LSD, is a "mixture or substance containing a detectable amount" of LSD. Since neither the statute nor the Sentencing Guidelines define "mixture," and it has no established common law meaning, it must be given its ordinary meaning, see Moskal v. United States, 498 U.S. 103, 108, which is "a portion of matter consisting of two or more components . . . that however thoroughly commingled are regarded as retaining a separate existence," Websters Third New International Dictionary. The LSD crystals left behind when the solvent evaporates are inside of the paper, so they are commingled with it, but the LSD does not chemically combine with the paper and, thus, retains a separate existence. Using the dictionary definition would not allow the clause to be interpreted to include LSD in a bottle or in a car, since, unlike blotter paper, those containers are easily distinguished and separated from LSD. Nor is there a reason to resort to the rule of lenity to construe the statute in petitioners favor, since a straightforward reading of 841(b) does not produce a result so absurd or glaringly unjust as to raise a reasonable doubt about Congress intent. Pp. 461-464.

2. This statutory construction is not unconstitutional. Determining the lengths of sentences in accordance with the LSD carriers weight is not arbitrary and, thus, does not violate due process. The pen