The knowledge related to the methodology of the FIELD trial study as a type of intervention studies, yet for many of our researchers is not fully understood. The aim of the current study was a better understanding of conducting this type of research. FIELD trial studies are done on healthy individuals and aim to prevent. These types of studies such as clinical trials are performed on both individual and collective levels. One type of these studies is Community Intervention Trial which is usually done on a large scale population. FIELD trial study should be carried out in stages, such as the formulation of hypotheses, selection of the population (reference population, study population, and sampling), measuring the baseline variables (before conducting preventive intervention), random allocation of subjects to intervention and control groups, doing interventions and measuring outcome. The methodology of FIELD trial studies is very similar to clinical trials. The difference is that FIELD trials are conducted on healthy individuals and aim to prevent and also the sample size required to this type of study is relatively more, and these studies are usually time consuming and costly.