Our current understanding of muscle and adipose tissue development has been largely restricted to the study of murine myogenic and adipogenic cell lines, since attempts to establish these cell lines from other species have met with only limited success. Here we report that a spontaneously immortalized bovine embryonic fibroblast cell line (BEFS) undergoes differentiation into adipogenic or myogenic lineages when ectopically transduced with PPAR gamma 2 (an adipogenic lineage determinant) or MyoD (a myogenic lineage determinant) and grown in adipogenic and myogenic differentiation culture media (ADCM and MDCM, respectively). We also found that PPAR gamma 2-overexpressing BEFS cells (BEFS-PPAR gamma 2) grown in ADCM with or without the PPAR gamma 2 ligand, troglitazone, preferentially differentiate into adipogenic cells in the presence of ectopic MyoD expression. Ectopic expression of PPAR gamma 2 in the inducible MyoD-overepxressing BEFS cells (BEFS-TetOn-MyoD) completely suppresses myogenic differentiation and leads to a significant increase in adipogenic differentiation, suggesting that the adipogenic differentiation program might be dominant. Therefore, BEFS, BEFS-PPAR gamma 2, and BEFS-TetOn-MyoD would be a valuable biological model for understanding a fundamental principle underlying myogenic and adipogenic development, and for isolating various genetic and chemical factors that enable muscle and adipocyte differentiation.