Rap mogul Dr. Dre is suing his former pal and author Bruce Williams over an unpaid loan.

The hip-hop icon, real name Andre Young, filed a lawsuit in Los Angeles County Superior Court on Tuesday, claiming he once loaned Williams - the author of Dre biography Rollin' With Dre - $101,377.85.

Dre alleges he's yet to receive the money back - and is demanding repayment in the legal papers, reports TMZ.com.

The case continues.