Plant phenolics in bmr sorghum lines were evaluated in bmr-6, bmr-12 or stacked near isogenic lines in two different backgrounds, RTx430 and Wheatland. There was considerable variation in HPLC profiles of soluble fractions obtained from younger internodes versus older internodes. GCMS revealed that 4-coumaric acid (4CA) was the dominant phenolic acid in wild-type (WT) plants. In contrast, ferulic acid (FA) in bmr-6 plants was found in greatest abundance, whereas bmr-12 plants had approximately equal levels of free 4CA and FA in plant stems. Near-isogenic lines containing both bmr-6 and bmr-12 genes displayed the greatest diversity in free phenolic acids, although their profiles were dominated by FA. Alkaline hydrolysis of washed cell walls indicated that WT plants possessed significantly higher levels of 4CA relative to FA as compared with bmr lines. In both genetic backgrounds, bmr-6 and bmr-12 resulted in lowered amounts of both phenolic acids. The ratio of 4CA/FA was greater in Wheatland-bmr-6 plants than that observed in RTx430-bmr 6 plants. In Wheatland plants containing both bmr-6 and bmr-12 (stacked), 4CA and FA levels in cell-wall-bound fractions were similar to near-isogenic bmr-6 plants. Whereas in RTx430 stacked plants, phenolic acid profiles were more similar to that found in RTx430 bmr-12 near-isogenic plants. Light microscopy of stem sections from Wheatland plants indicated lignification of the cortical sclernechyma and vascular bundle fibers in WT plants. In bmr-6 plants lignification patterns were similar to those in WT plants, but the extent and density of staining was reduced. Overall lignification in bmr-12 plants was reduced, especially in the fibers enclosing the vascular bundles. Lignification was strongly diminished in stacked plants. This is the first known report that emphasizes the interactions of bmr traits and genetic background on changes to cell wall associated phenolics in sorghum.