Review of the literature clearly illustrated the need for more information on journal bearings operating in the transition vortex regime. Especially in the light of recent information indicating that many real applications may be operating in this region and to date most consideration has been given to fully turbulent studies. Accordingly, an experimental test rig was designed to measure torque and both circumferential and axial pressure profiles. The test bearing was circular and of central circumferential supply groove design. LID ratio was 0.25 for each land and a clearance ratio of 0.00307 used to conform with "real" modelling of high speed bearings. Lubricant inlet and outlet temperature were measured (with Rem based on the latter) together with shaft speed and displacement. Three lubricants were used, Tellus 22, Tellus RIO and water to allow a Reynolds number range of 30 - 10, 000 to be covered, and thus encompassing lamina_r, transition and turbulent flow regimes. Low Reynolds number results agreed well with laminar theory and transition from laminar to vortex flow was observed to occur around the speed predicted by Taylor. In the transition region, inertial effects were found to be very small but were taken into consideration for all comparisons between theory and experiment. Existing super laminar theories were in poor agreement with experiment. An empirical theory based on friction factor results was developed including inertia and led to much improved estimates of circumferential pressure distribution. The best agreement being observed in the mid transition region were a "hump" in the friction factor v's Reynolds number results had been measured. Due to the method of measuring pressure profiles interesting observations are reported on cavitation phenomena.