This protocol describes a method to assess concentrations of free cytoplasmic calcium, [Ca2+]i, in cultured adherent RAW 264.7 cells, using a 96- well plate format. This objective is accomplished by using the Ca2+-sensitive fluorescent dye, fluo-3, which permeates cell membranes as an ester and is
hydrolyzed in the cell to its Ca2+-sensitive acidic form. Fluorescence for the adherent cells is measured over time by using a bottom read of a 96-well plate, with cells that have been washed.