The aim of this studywas totest iffurther grinding of corn DDGS isadvantageous in terms of apparent total tract digestibility (ATTD) of DM, GE, nitrogen (N), and NDFingrowing and finishing pigs.It was also tested to determine if ATTD was different between hammermill and roller millgrinding methods.There were 3 diets. Each diet consisted of 51% corn ground at 500 microns with a roller mill, and 45% of corn DDGS ground at 450 microns using a hammermill, or 45% corn DDGS ground at 450 microns using a roller mill,or 45% of corn DDGS not further ground (unprocessed) at 650 microns.Results show thatparticle size reduction either with a roller mill or a hammermill (from 650 to 450 microns) increasedATTDof GE and DM of corn DDGS, tended to increase ATTD of N,but had no effect on ATTD of NDF. Finishing pigs had grater ATTD of GE and CP thangrowing pigs (tended to be greater for ATTD of DM). There were no effectsof growth stage in ATTD of NDF.There were no interactions betweenparticle size reduction and growth stage.In conclusion, reduction of particle size of corn DDGS (650 to 450 microns) either with a roller or with a hammermill has a beneficial effecton digestibilityof valuable dietary components in growing and finishing pigs.