Diet is a potentially modifiable risk factor for diabetes. Dietary patterns may exert greater effects on health than individual foods, nutrients or food groups. Data on associations between dietary patterns and the risk of insulin resistance and type 2 diabetes are sparse. The aim of the study was to examine associations between dietary patterns and the risk of insulin resistance.We performed a cross sectional study involving a group of 1018 men and women, sampled from 17 general practice lists in the South of Ireland, with a response rate of 69%. Participants completed a detailed health and lifestyle questionnaire and provided fasting blood samples for analysis of glucose, insulin and lipids. Dietary intake was assessed using a food frequency questionnaire. The food frequency questionnaire was a modification of the UK arm of the European Prospective Investigation into cancer, EPIC study, which was based on that used in the US Nurses' Health Study. Dietary patterns were assessed by K cluster analysis. Insulin resistance was estimated on the basis of fasting glucose and insulin, using the glucose homeostasis model (HOMA scores). Insulin resistance was defined as the upper quartile of the HOMA scores. Three dietary patterns were identified by cluster analysis (traditional Irish diet, a prudent diet and an alcohol and convenience foods diet). Participants in clusters 1 (traditional Irish diet) and 3 (high alcohol and convenience foods) had a lower intake of more 'healthy' food groups (such as fruit, vegetables, low fat dairy products, poultry, fish and whole grain products) and higher intake of foods richer in total and SFA content (such as high fat dairy products, butter, meat and meat products). Cluster 2 (prudent dietary pattern) was characterized by a higher intake of food groups that are typically recommended in health promotion programs and a lower intake of meat (read meat), meat products, sweets, high fat dairy and white bread (white bread and unrefined cereal). The prudent diet had the lowest HOMA scores in analysis of covariance. The prevalence of insulin resistance in the prudent diet was lower than that in the traditional diet (OR=0.53; 95%CI, 0.33-0.85 in fully adjusted analysis).A prudent diet may be associated with enhanced insulin sensitivity and a lower risk of type 2 diabetes.