This paper discusses approaches to the problem of pest control decision making. A farmer's pest control decisions are shown to depend on his subjective perception of the pest hazard, the controls he recognises as available to him, his subjective estimate of their net effect, and his individual decision rule or goal. A case study is discussed in which a decision model is used to compare objective pest observation with subjective perceptions of sugar beet growers. Applications of such a model for improving pest control decisions are suggested.