Because field trials often necessitate less detailed measurments than are possible in a true research environment, they are often believed to represent a poorer form of science. However, this is a very short-sighted view because there are particular benefits to be derived from carefully designed and conducted field trials which cannot be satisfied by smaller, more detailed studies.Within the context of reproduction research the objective is to understand the basic physiological mechanisms controlling reproduction, and to identify the nature and extent of reproductive wastage and its causes. The logical extension of this is to develop appropriate treatment strategies to overcome these limitations, some of which may be satisfied by changes in animal management while others will require recourse to pharmaceutical manipulation.