Abstract: A cuvette for the measurement of the absorption of irradiation in liquid samples which at least in the regions of the windows is of a transparent plastic with an inner space which is formed in an essentially box-shaped upper part with an upper opening for filling and removing sample fluid and in an essentially box-shaped lower part which projects downwards from the floor of the upper part and which comprises a smaller cross section than the upper part, of maximally 200 &mgr;l content capacity, two pairs of planar-parallel windows in the lower part which lie opposite one another, wherein the distance a of the one pair is different to the distance b of the windows of the other pair in order to make available differing layer thickness of the sample fluid for the measurement and with four feet which are flush with the four corners of the upper part and which extend away from the upper part at least until up to the level of a floor of the lower part.