Abstract: An apparatus for determining the concentrations of n hemoglobin derivatives in a sample of undiluted, unhemolyzed whole blood provided in a cuvette, employs a device producing a primary light beam formed of at least n substantially monochromatic, narrow-band components of different wavelengths. Further provided is a detection device for measuring of the radiation passing through the cuvette. At least two measuring geometries are provided for spectral detection of a collimated central beam and at least one scatter beam, and detection of the central beam departing from a first measuring location in the cuvette takes place in a first measuring position on the axis of the primary beam, and detection of the scatter beam takes place in a second measuring position if it departs from the first measuring location in the cuvette, or in the first measuring position if it departs from a second measuring location in the cuvette, whereby the axes of the central beam and the scatter beam(s) enclose angles .alpha..sub.