Integrins regulate cell growth, differentiation, and behavior in many systems. Integrin beta(1C) (beta(1S)) is an alternatively spliced variant of integrin beta(1) with a specific cytoplasmic domain and is expressed in several human tissues. Human beta(1C) transiently expressed in mouse 10T1/2 fibroblasts showed a diffuse pattern of cell surface staining, whereas beta(1) localized to focal adhesions. Moderate concentrations of beta(1C) had no effect on actin stress fibers or focal adhesions, but markedly inhibited DNA synthesis. Inhibition by beta(1C) mapped to the late G(1) phase of the cell cycle, near the G(1)-S boundary. Thus, alternative splicing of beta(1) results in transmission of distinct signals that may regulate growth in vivo.