Although it has been known for many years that β1 integrins undergo differential glycosylation in accordance with changes in cell phenotype, the potential role of N-glycosylation as a modulator of integrin function has received little attention. One reason for the relatively limited interest in this topic likely relates to the fact that much of the prior research was correlative in nature. However, new results now bolster the hypothesis that there is a causal relationship between variant glycosylation and altered integrin activity. In this review, the evidence for variant glycosylation as a regulatory mechanism for β1 integrins are summarized, with particular emphasis on: (1) outlining the instances in which cell phenotypic variation is associated with differential β1 glycosylation, (2) describing the specific alterations in glycan structure that accompany phenotypic changes and (3) presenting potential mechanisms by which variant glycosylation might regulate integrin function. © 2004 Elsevier B.V. All rights reserved.