To explore whether Farmers' Locus of Control (LOC) could be useful in agricultural extension programmes to improve managerial ability. This test records a farmer's belief in her/his control over production outcomes. A mail survey of 2300 New Zealand farmers was used to obtain a range of variables, and to measure their LOC using a question set created from farming situations and terminology. Using regression analysis the farmer LOCs were related to many variables including the Farmers' self assessment of his/her managerial ability as well as their true ability. The LOC had adequate reliability and consistency. The analysis indicated LOC measures some independent characteristics of farmers as its prediction from other variables is by no means perfect. Furthermore, LOC proved to be partially related to a range of output variables. This indicates a farmer's LOC originates in part from fundamental personality traits which in turn relate to managerial ability. When the fundamental variables are available they can be used to help explain, and improve, managerial ability. However, extension programme efforts to change a farmer's view of his control (LOC) will have benefits as, when considered on its own, a farmer's LOC is still related to successful outcomes. Furthermore, LOC may be related to other aspects of farming such as the general satisfaction obtained. The LOC test provides benchmarks to assess Farmers' control belief, and improvements from training. (Contains 3 tables and 1 figure.)