Etiological hypotheses related to diet and life style can be best addressed in prospective cohort studies, in which measurement error can be reduced and recall bias is minimal. From 2002 to 2003, a pilot study of 1057 subjects was conducted by the Digestive Disease Research Center (DDRC) of Tehran University of Medical Sciences in collaboration with IARC and the US National Cancer Institute (NCI) to evaluate the logistical aspects of establishing a prospective study in Golestan.  The aims of the pilot study were to assess the response rate of the study population, to develop valid and reliable methods for assessing nutritional, anthropometric and life style factors, to develop follow-up methods to ascertain mortality and cancer incidence among the enrolled subjects, and to establish efficient procedures for collecting and storing biological samples.  Results of the pilot study confirmed the feasibility of conducting a prospective cohort study in Golestan.The related published papers of pilot study are addressed in “Published Papers” subdivision.