Laccases (P-diphenol:O2 oxidoreductase; EC 188.8.131.52), also termed laccase-like multicopper oxidases, are blue copper-containing oxidases which comprise multigene families in plants. In the Arabidopsis thaliana genome, 17 laccase genes (LAC1 to LAC17) have been annotated. To identify laccases involved in cell wall biosynthesis in Arabidopsis primary stems we have developed homozygous T-DNA mutants for 14 individual laccases. Six laccases are highly expressed in the wild type primary stem, four of which (LAC2, LAC4, LAC12, and LAC17) show correlated gene expression with one to several genes (e.g., cellulose synthases) involved in biosynthesis of the plant cell wall. Both tissue specific and non-specific expression was observed across the laccases and expression of LAC2 and LAC12 seemed to be specific to primary stems. In agreement with previous studies, the transparerent testa phenotype was observed for LAC15 T-DNA mutant seeds and an approximate 24 hour delay in germination was observed for these seeds. An approximate 20% reduction in glucose, galactose, and xylose was observed in primary stem cell walls of the LAC2 T-DNA mutants while similar relative increases in xylose were observed for LAC8 and LAC13 T-DNA mutants. Lignin content (both total lignin and Klason lignin) were not altered in any of the laccase T-DNA mutants. However, monolignol composition was altered in primary stem cell walls of LAC15 and LAC17 T-DNA mutants. Our results indicate that individual laccases are involved in quite different and distinct biochemical pathways and that laccases might be involved in polymerization of both polysaccharides and monolignols in the Arabidopsis cell wall.