Interest in developing CIRA reference models of trace species has stemmed largely from five COSPAR workshops held every two years since 1986. Two previous models have been published namely CIRA Part I (Thermosphere Models) CIRA Part II (Middle Atmosphere Models) and now CIRA Part III (Trace Constituent Reference Models). The trace consituent reference models presented here are of trace species in the stratosphere, mesosphere and lower thermosphere which play important roles in controlling the chemistry, radiation budget and circulation patterns of the atmosphere. These models of the climatology of trace species are considered to be reference models rather than standard models and therefore it is not crucial that they be correct in an absolute sense. The models presented represent a benchmark of conditions in the early 1980s and can be compared with present and future observations as an indication of constancy or change in the atmosphere. The