Engineering thermoplastics have greatly improved over the last decade. As a result of these improved performance characteristics and their becoming more cost competitive with traditional cage materials, their use in tapered roller bearing cages has become a reality. Design flexibility, lighter weight, resistance to handling damage, etc. make them attractive. This paper does point out certain characteristics of thermoplastics which must be taken into consideration thus influencing the choice of material and what environments they can endure. Compatibility with lubricants at elevated temperatures, growth from moisture and thermal expansion, solvent resistance, impact resistance, strength and dimensional stability are the major considerations. Thermoplastics have found a place in the tapered roller bearing family.