delivered the opinion of the Court.
This ease asks us to consider whether 21 U. S. C. § 846, the drug conspiracy statute, requires the Government to prove that a conspirator committed an overt act in furtherance of the conspiracy. We conclude that it does not.
I
According to the grand jury indictment, Reshat Shabani participated in a narcotics distribution scheme in Anchorage, Alaska, with his girlfriend, her family, and other associates. Shabani was allegedly the supplier of drugs, which he arranged to be smuggled from California. In an undercover operation, federal agents purchased cocaine from distributors involved in the conspiracy.
Shabani was charged with conspiracy to distribute cocaine in violation of 21 U. S. C. § 846. He moved to dismiss the indictment because it did not allege the commission of an overt act in furtherance of the conspiracy, which act, he argued, was an essential element of the offense. The United States District Court for the District of Alaska, Hon.. H. Russel Holland, denied the motion, and the case proceeded to trial. At the close of evidence, Shabani again raised the issue and asked the court to instruct the jury that proof of an overt act was required for conviction. The District Court noted that Circuit precedent did not require the allegation of an overt act in the indictment but did require proof of such an act at trial in order to state a violation of § 846. Recognizing that such a result was “totally illogical,” App. 29, and contrary to the language of the statute, Judge Holland rejected Shabani’s proposed jury instruction, id., at 36. The jury returned a guilty verdict, and the court sentenced Shabani to 160 months’ imprisonment.
The United States Court of Appeals for the Ninth Circuit reversed.
Chief Judge Wallace wrote separately to point out that in no other circumstance could the Government refrain from alleging in the indictment an element it had to prove at trial. He followed the Circuit precedent but invited the Court of Appeals to consider the question en banc because the Ninth Circuit, “contrary to every other circuit, clings to a problematic gloss on 21 U. S. C. § 846, insisting, despite a complete lack of textual support in the statute, that in order to convict under this section the government must prove the commission of an overt act in furtherance of the conspiracy.”
*13 II
Congress passed the drug conspiracy statute as §406 of the Comprehensive Drug Abuse Prevention and Control Act of 1970, Pub. L. 91-513, 84 Stat. 1236. It provided: “Any person who attempts or conspires to commit any offense defined in this title is punishable by imprisonment or fine or both which may not exceed the maximum punishment prescribed for the offense, the commission of which was the object of the attempt or conspiracy.”
Id.,
at 1265. As amended by the Anti-Drug Abuse Act of 1988, Pub. L. 100-690, § 6470(a), 102 Stat. 4377, the statute currently provides: “Any person who attempts or conspires to commit any offense defined in this subchapter shall be subject to the same penalties as those prescribed for the offense, the commission of which was the object of the attempt or conspiracy.” 21 U. S. C. § 846. The language of neither version requires that an overt act be committed to farther the conspiracy, and we have not inferred such a requirement from congressional silence in other conspiracy statutes. In
Nash
v.
United States,
Nash
and
Singer
follow the settled principle of statutory construction that, absent contrary indications, Congress intends to adopt the common law definition of statutory terms. See
Molzof
v.
United States,
As to those views, we find it instructive that the general conspiracy statute, 18 U. S. C. § 371, contains an explicit requirement that a conspirator “do any act to effect the object of the conspiracy.” In light of this additional element in the general conspiracy statute, Congress’ silence in § 846 speaks volumes. After all, the general conspiracy statute preceded and presumably provided the framework for the more specific drug conspiracy statute.
“Nash
and
Singer
give Congress a formulary: by choosing a text modeled on §371, it gets an overt-act requirement; by choosing a text modeled on the Sherman Act, 15 U. S. C. § 1, it dispenses with such a requirement.”
United States
v.
Sassi,
*15
Early opinions in the Ninth Circuit dealing with the drug conspiracy statute simply relied on our precedents interpreting the general conspiracy statute and ignored the textual variations between the two provisions. See
United States
v.
Monroe,
What the Ninth Circuit failed to recognize we now make explicit: In order to establish a violation of 21 U. S. C. § 846, the Government need not prove the commission of any overt acts in furtherance of the conspiracy.
United States
v.
Felix,
Shabani reminds us that the law does not punish criminal thoughts and contends that conspiracy without an overt act requirement violates this principle because the offense is predominantly mental in composition. The prohibition against criminal conspiracy, however, does not punish mere thought; the criminal agreement itself is the
actus reus
and has been so viewed since
Regina
v.
Bass,
11 Mod. 55, 88 Eng. Rep. 881, 882 (K. B. 1705) (“[T]he very assembling together was an overt act”); see also
Iannelli
v.
United States,
*17
Finally, Shabani invokes the rule of lenity, arguing that the statute is unclear because it neither requires an overt act nor specifies that one is not necessary. The rule of lenity, however, applies only when, after consulting traditional canons of statutory construction, we are left with an ambiguous statute. See,
e. g., Beecham
v.
United States,
As the District Court correctly noted in this case, the plain language of the statute and settled interpretive principles reveal that proof of an overt act is not required to establish a violation of 21 U. S. C. § 846. Accordingly, the judgment of the Court of Appeals is
Reversed.
Notes
See
United States
v.
Sassi,
