The differentiation of chondrocytes and of several other cell types is associated with a switch from the -_6B to the -_6A isoform of the laminin -₆-₁ integrin receptor. To define whether this event plays a functional role in cell differentiation, we have used an in vitro model system that allows chick chondrogenic cells to remain undifferentiated when cultured in monolayer, and to differentiate into chondrocytes when grown in suspension culture. We report that: i. upon overexpression of the human -_6B, adherent chondrogenic cells differentiate to stage I chondrocytes (i.e. increased type II collagen, reduced type I collagen, fibronectin, -₅-₁ and growth rate, loss of fibroblast morphology); ii. the expression of type II collagen requires the activation of p38 MAP kinase; iii. the overexpression of -_6A induces an incomplete differentiation to stage I chondrocytes, whereas no differentiation was observed in -₅ and mock transfected control cells; iv. a prevalence of the -_6A subunit is necessary to stabilize the differentiated phenotype when cells are transferred to suspension culture. Altogether, these results indicate a functional role for the -_6B to -_6A switch in chondrocyte differentiation: the former promotes chondrocyte differentiation, whereas the latter is necessary to stabilize the differentiated phenotype.