A system for growing three-dimensional cell culture has been developed which exhibits many features of solid tumours. This system comprises cells growing as a thick mat on a semipermeable membrane suspended in stirred media. SiHa cells grown as these multilayered cell cultures (MCCs) have produced cultures up to ca. 20 cell diameters in thickness. The MCCs, like solid tumours growing in vivo. develop diffusion-dependent necrosis and hypoxia and the cell packing acts as a barrier to the diffusion of drugs. These cultures can, therefore, be used to study aspects of cancer biology and drug transport that are difficult to study using other techniques.