In the present invention cells are placed in a multiwell plate and grown. When the assay is to be performed, one uses gravity to wash away any unbound ligands rather than vacuum or centrifugation. The cells are then examined to detect the bound ligand. To perform the washing step(s) the plate is placed into a carrier plate having open wells in register with the wells of the filter plate or one may use a wicking device or an underdrain attached to the bottom of the filter plate. Sufficient wash liquid is added to allow for filtration by the effect of gravity to occur. Cells are retained within the wells at a rate of 4 times that of other rapid methods.