The cost effectiveness of using aspheric surfaces in infrared systems is reviewed. In particular, two design studies are described, the first of a Maksutov-type objective and the second of a high numerical aperture pyroelectric vidicon objective. In the first case, the use of first one and then two aspheric surfaces results in an increasing ability to satisfy all of the aberration and dimension requirements of its specification. In addition, a size versus raw material trade-off becomes possible. In the second case, a four-element spherical design is compared with a two-element aspheric design over a large range of numerical apertures. The analysis demonstrates that the improved transmission and reduced materials costs that result from the use of aspheric surfaces outweigh the cost of aspheric manufacture. The paper concludes that in the cases examined, aspherics are highly cost effective, provided that a facility for diamond machining to an optical finish, without subsequent polishing, is available.