The paper describes the design and evaluation of ad-hoc extensions to the IEEE 802.15.3 medium access control (MAC) layer for wireless personal area networks (WPANs). The proposed protocol allows communication between ad-hoc devices without the intervention of any central entity and, at the same time, ensures bounded delays for isochronous traffic. Ad-hoc communication is made possible without the hidden terminal problem. Features from both IEEE 802.15.3 and IEEE 802.11 standards are used - in particular the TDMA structure from 802.15.3 and RTS-CTS based contention from 802.11. The protocol includes certain other ingredients, like a decentralized synchronization procedure using randomized beaconing, periodically interspersed contention periods, bit maps to convey reservation information and a mechanism to estimate and react to channel errors. The MAC has been simulated in ns-2 and simulation results are reported.