Wireless technologies are being widely used today across the globe to support the communication needs of very large number of end users for voice communications and data services. Data services include activities such as sending e-mails, instant messages and accessing the Web. Due to an increased demand the network becomes congested. The congestion control mechanism in Transmission Control Protocol (TCP) is designed for wired networks. Due to the inherent characteristics of wireless networks, TCP when applied to wireless networks suffers from poor performance because of random loss, burst loss and packet reordering and therefore needs modification from the original protocol. This thesis proposes two enhancements in the TCP Vegas algorithm. The EnhancedVegas and NewVegas algorithms control the congestion in MANETs. An enhancement in MAC layer protocol called CTMAC-F protocol is proposed to control collision in the MAC layer. GPSR routing protocol is used for an efficient routing in adhoc networks. All these provide an integrated layer approach technique to mitigate congestion and collision with efficient routing in adhoc networks.