Schering-Plough Corp. said Tuesday it has agreed to pay $435 million and will plead guilty to conspiracy to settle a federal investigation into its drug sales and marketing practices and its clinical trial programs.

Kenilworth, N.J.-based Schering-Plough said it will pay $255 million to resolve civil aspects of the previously disclosed investigation. A subsidiary, Schering Sales Corp., will pay a criminal fine of $180 million and plead guilty to one count of conspiracy under the agreement, which is subject to court approval.