This document specifies a real-time transport protocol (RTP) payload format to be used for the Variable-Rate Multimode Wideband (VMR-WB) speech codec. The payload format is designed to be able to interoperate with existing VMR-WB transport formats on non-IP networks. A media type registration is included for VMR-WB RTP payload format. VMR-WB is a variable-rate multimode wideband speech codec that has a number of operating modes@ one of which is interoperable with AMR-WB (i.e.@ RFC 3267) audio codec at certain rates. Therefore@ provisions have been made in this document to facilitate and simplify data packet exchange between VMR-WB and AMR-WB in the interoperable mode with no transcoding function involved.