An apparatus for the calibration and quality assurance of a multichannel spectrophotometer, particularly an ELISA spectrophotometer, comprises a series of filters having a known first color and linearly increasing optical density. The response of the spectrophotometer is measured against the known color and linearly increasing optical density. Additional filters of at least one additional color permit checking the color response of the spectrophotmeter. An algorithm determines whether the response conforms to predetermined conditions. An output is produced to provide a record of the calibration and quality assurance of the spectrophotometer. The invention has particular utility for conducting calibration and quality assurance of ELISA spectrophotometers used in clinical laboratory screening for infectious diseases, such as Hepatitis B and the AIDS viruses.