A quail cell line (QT6-c) was co-transfected with pTEX vector expressing RNA complementary to chicken integrin beta 1 subunit mRNA (Anti-Int) and pRSVneo vector by a calcium phosphate method. Transfectants showing reduced expression of quail integrin beta 1 subunit were selected with an immunoblot assay, and a few positive clones were examined in detail. Northern blot and immunoblot analyses revealed that the Anti-Int caused a clear reduction of the transcript encoding integrin beta 1 subunit depending on culture conditions. The number of cell surface integrins also decreased in proportion to the decrement of the total amount of integrin beta 1 subunits. When one transfectant (QA23) was cultured in a serum-free medium, cell shape changed from fibroblast-like to neuron-like morphology accompanied by a low growth rate, and the cells did not form focal contact on fibronectin. A similar morphological change occurred in QT6-c cells when the cells were infected with Rous Sarcoma virus, which could produce the Anti-Int. The QA23 cells did not attach to fibronectin as efficiently as did the original QT6-c cells. These data suggest that reduced expression of integrin beta 1 subunit affects cell growth as well as cell morphology by disordering the interaction between integrins and matrix proteins and/or cytoplasmic proteins.