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Consumption of navy beans is associated with positive health outcomes including improvement of blood glucose control and blood lipid profile. The formulation of foods with added pulse flours may provide some health benefits known for whole pulses. However, pulse flours available on the market represent a broad range of products varying in their processing. <u>The objective</u> of this project was to evaluate the carbohydrate digestion rate in navy bean flours varying in particle size and to determine whether these properties were affected by thermal processing. <u>Methods</u>: navy bean flours were produced by Canadian International Grain Institute using pin milling of raw navy beans to the following fractions (mean particle size, µm): coarse (C, 1101.6), regular (R, 630.7), fine (F, 301.7), very fine (VF, 144) and superfine (SF, 26.8). Raw or cooked flours (baked at 350°F for 12 min) that were subsequently masticated and minced were used in the experiment. Carbohydrate digestion rate was determined via simulated digestion of flour samples conducted in triplicate over 180 min using modified Englyst method. The released glucose was assayed using hexokinase method. <u>Results</u>: There was a significant effect of particle size on carbohydrate digestion rate in raw (P<0.0001) and cooked flours (P<0.0001). For raw flours, area under the curve (AUC) for glucose was 13065, 16723, 19857, 24259 and 33488 mg/mL×min for C,R,F,VF and SF fractions, respectively. For cooked flours, AUC for glucose was 8247, 9096, 19180, 23581 and 32799 mg/mL×min for C,R,F,VF and SF fractions, respectively. Particle size was inversely correlated with glucose AUC for both raw and cooked flours (r=-0.9, P<0.0001). <u>Conclusion: </u> particle size of navy bean flours obtained by dry milling method predetermines carbohydrate digestion rates as measured in vitro and this relationship is sustained after dry-heat cooking.