A comparison was made of various lubricant types regarding their ability to effectively lubricate aluminum-on-tool steel under very high loads. An anvil friction tester in conjunction with a laboratory press was employed to apply pressures up to 260,000 psi to the test pieces. Of all materials studied, natural waxes showed the optimum lubricating ability. It appears that this behavior can be attributed to the unusual rheological character of the waxes. On the other hand, silicone fluids exhibited only marginal improvements over dry (unlubricated) aluminum-on-steel. These results tend to support the view that chemical factors rather than pressure/viscosity effects control the lubrication of aluminum-on-steel.