The effects of feeding graded levels (0, 4, 8, 12%) of pectin (water soluble nonstarch polysaccharide, NSP) and cellulose (8%, water insoluble NSP) on lysine (LYS) and threonine (THR) utilization for body protein deposition (PD) in growing pigs was investigated. True ileal amino acid (AA) digestibility (TID) was not influenced ('P' > 0.10) by pectin intake, while ileal endogenous AA losses (ENL) increased linearly ('P' < 0.05) with diet pectin level. Consequently, apparent ileal AA digestibility (AID) decreased linearly ('P' < 0.05) with dietary pectin level. For extreme dietary pectin levels AID of LYS and THR differed by 5.7% and 4.5%, respectively. Including cellulose in the diet did not influence ('P' > 0.10) AID, TID or ENL of AA. Pectin intake reduced (' P' < 0.05) the utilization of AID THR, but not LYS, intake for PD. The difference in THR utilization between extreme dietary pectin levels was 9%. When increasing the fiber level in pig diets, the minimum AID dietary THR to LYS ratio should be increased.