The preferred orientations and microstructures of the cold rolled 0.004%C and 0.022%C steel were studied. The crystallographic deformation theory was applied to analyse the results of the x -ray measurements and TEM observations. It was found that the rolling texture of the steels could be described by a {111}//ND fiber and a $lt;110$gt;//ND fiber. The equiaxed cells developed by homogeneous slip might be a major deformation mechanism of the steels at low rolling reductions. At medium to high rolling reductions, however, the major deformation mechanism was changed to the formation of the microbands, which was developed by a localized inhomogeneous slip. As further increasing reduction, the deformation mechanism was changed consecutively as clustering of microbands, decreasing microband thickness, a rotation of microbands to the rolling direction and a development of shear bands in the hard grains.