Small patches of polyethylene terephthalate (PET) nonwoven microfibrous matrices have excellent properties and can be used as carriers for culturing cells in agitated bioreactors. The microfibrous carriers are highly porous and can provide large surface areas and three-dimensional space for high-density cell growth. In this work, the microfibrous carriers and several commercial microcarriers were used to study cell attachment kinetics, growth, and monoclonal antibody production with Chinese hamster ovary cells. Compared with commercial solid and macroporous microcarriers, the microfibrous carriers showed better or similar performances. In addition, the microfibrous carriers provided a wider operable range for agitation rate than commercial microcarriers, effectively protecting cells from shear stress and carrier collisions. In addition, the microfibrous carriers are available at a much lower cost than commercial microcarriers, providing an attractive alternative to microcarrier-based large-scale cell cultures. (C) 2011 American Institute of Chemical Engineers Biotechnol. Prog., 27: 1126-1136, 2011