Several integrin alpha subunits have structural variants that are identical in their extracellular and transmembrane domains but that differ in their cytoplasmic domains. In the present study, we examined the possibility that the A and B variants of the alpha 6 beta 1 integrin laminin receptor differ in function. P388D1 macrophages that had been transfected with the alpha A integrin subunit were 3-4 fold more migratory than P388D1 macrophages that had been transfected with the alpha 6 B integrin subunit. Deletion of the alpha 6 cytoplasmic domain markedly inhibited the ability of the alpha 6 beta 1 receptor to promote migration.