For more than 25 years the Lambda ratio (λ) has been used as an indicator of the lubricant regime in an operating contact within either bearings or gear sets. λ is determined when the lubricant film thickness (h) within the contact is divided by the composite roughness (σ) of the two surfaces forming the contact. Recommendations of appropriate film thickness equations and surface roughness values are made to provide a modified lambda ratio (λm) that better represents the lubricant regime within bearings or gears.In recent years bearing performance, especially as related to fatigue life, has increased significantly. This is primarily due to cleaner steels but also from better surface finishes and bearing internal geometries. With λm and an understanding of how contact fatigue damage mode relates to a wide range of λm values, it may be possible to provide gear sets with improved performance similar to that now available in bearings.