Book excerpt: The place and potential for sheep em tropical and subtropical regions; Available genetic resources: the origin and classification of the world's sheep; Improvement programs; Nutrient requirement of hair sheep in tropical and subtropical regions; Forage resources in northeast Brazil: their value and management; Supplemental feed resources and their utilization by hair sheep; Reproduction in sheep; Herd health management of sheep in the semiarid tropics; Facilities and installations for hair sheep production; Products and marketing; Tropical sheep production systems; Some suggestions for improved productivity through management; Recommendations for further research.