A method is described by which the growth inhibitory effects of cytotoxic compounds on exponentially growing adherent cell lines can be quantitated. Cultures are established in microtiter plates and the cytotoxic compounds to be tested are added after 2 days. Dilution series are constructed within the microcultures using 8-channel micropipets designed for use with microtiter plates. To measure growth after several days of drug exposure, adherent cell layers are fixed, stained, and the plates washed in water to remove excess stain. After stained cells are air-dried and solubilized, absorbance is determined using spectrophotometers designed for reading of microtiter trays. This method is reproducible and offers the advantage that any adherent cell line can be utilized without the need for tedious cell-counting procedures.