OPINION

Shawn Lee Allen appeals his conviction and 151-month sentence for conspiracy to distribute more than fifty grams of cocaine base, in violation of 21 U.S.C. § 846 (2000). Allen first challenges the sufficiency of the evidence supporting his conspiracy to distribute cocaine base conviction. He argues that no physical evidence such as drugs, photographs, tapes, or fingerprints were presented at trial, and therefore the evidence is insufficient. However, physical evidence is not required to prove involvement in a drug distribution conspiracy. Allen’s coconspirators testified to Allen’s involvement in drug transactions spanning several years. Furthermore, a drug conspiracy is often proven entirely by such circumstantial evidence. See United States v. Burgos, 94 F.3d 849, 857 (4th Cir. 1996).

Allen also contends the district court demonstrated bias against him. However, he has presented no evidence of any improper statements or conduct by the district court.

Accordingly, we affirm Allen’s conviction and sentence. We dispense with oral argument because the facts and legal contentions were adequately presented in the materials before the court.

AFFIRMED.