Turbocharger manufacturers are increasingly required to produce higher boost pressure ratio compressors to satisfy the diesel engine market's demand for ever increasing specific power output. Package size constraints often prohibit the use of larger single stage or two stage installtions. This paper describes a compact and robust design of turbocharger which incorporates a small axial compressor stage mounted in front of, and close coupled to, a radial compressor of conventional design.The design and construction of this so called axial-radial turbocharger is described. Test results showing an improvement in both boost pressure ratio and usable map width are presented and discussed. Finally a method of further improving compressor map width is suggested.