Proceedings of the final research co-ordination meeting on Improving Sheep and Goat Productivity with the Aid of Nuclear Techniques, Perth, Australia, 20–24 February 1989, reporting the results of a five year co-ordinated research programme. The main objectives of this programme were (a) to encourage research aimed at establishing the nutritional value of locally available feedstuffs and assessing strategies for supplementation, and (b) to examine the reproductive patterns of small ruminants in different environments, with particular emphasis on the seasonality of ovarian and testicular function, and the effects of nutrition and disease on reproductive efficiency.