ANBL-6, a myeloma cell line, proliferates in response to interleukin 6 (IL-6) stimulation, coculture with bone marrow stromal cells, and when harboring a constitutively active mutant N-ras gene. Eighteen samples, including 4 IL-6-treated, 3 mutant N-ras-transfected, 3 normal stroma-stimulated, 2 multiple myeloma (MM) stroma-stimulated, and 6 untreated controls were profiled using microarrays interrogating 12 626 genes. Global hierarchical clustering analysis distinguished at least 6 unique expression signatures. Notably, the different stimuli altered distinct functional gene programs. Class comparison analysis (P =.001) revealed 138 genes (54% involved in cell cycle) that distinguished IL-6-stimulated versus nontreated samples. Eighty-seven genes distinguished stroma-stimulated versus IL-6-treated samples (22% encoded for extracellular matrix [ECM] proteins). A total of 130 genes distinguished N-ras transfectants versus IL-6-treated samples (26% involved in metabolism). A total of 157 genes, 20% of these involved in signaling, distinguished N-ras from stroma-interacting samples. All 3 stimuli shared 347 genes, mostly of metabolic function. Genes that distinguished MM1 from MM4 clinical groups were induced at least by one treatment. Notably, only 3 genes (ETV5, DUSP6, and KIAA0735) are uniquely induced in mutant ras-containing cells. We have demonstrated gene expression patterns in myeloma cells that distinguish an intrinsic genetic transformation event and patterns derived from both soluble factors and cell contacts in the bone marrow microenvironment.