The performance of two polymer-based materials (polyimide/MoS 2 and ptfe/ glass fibre/MoS 2) as self-lubricating cages for ball bearings has been comprehensively evaluated. The two composites emerged as the most promising for operating at elevated temperatures during screening tests in a thrust-bearing geometry and were then tested in four sizes of 440C stainless steel single-row radial ball bearings at a range of loads, speeds and temperatures. Two regimes of operation were observed: the first with essentially zero steel wear when the lubricant transfer film is complete and bearing life is dictated by cage wear; the second with finite steel wear when the transfer film is only partially effective and bearing life is dictated by increase in internal clearance. The ball/raceway stress at which steel wear starts to occur is very low (< 1.2 × 10 3 MN m −2) compared to the stress implied by the catalogue load capacity of the bearings. The ball/raceway stress also has an important effect on both steel wear rate and cage wear rate. Overall, the ptfe-based composite gave lower steel and cage wear than did the polyimide-based composite, but the latter could be operated at higher temperatures (up to 360° C) and at slow speeds it gave a higher load capacity before the onset of steel wear. Using the wear results as a basis, a Bearing Performance Guide has been produced which provides a convenient means of approximately predicting the bearing life over a wide range of operating conditions