An arrangement for measuring the diffuse reflection of samples and a method for internal recalibration of the measuring head. The spectrometric measuring head with a device for recalibration comprises a housing which is provided with a window and which contains an illumination source, a spectrometer arrangement and at least two standards for internal recalibration. The two standards can be swiveled into the beam path of the measuring head selectively so that the measurement light emitted by the illumination source can be used in its entirety for recalibration. A processor for acquiring and processing measured values and an interface to a bus system are arranged in the housing. Accordingly, relatively time-consuming calibration of the measuring head at the place of use is required only before putting into operation or at longer time intervals. By the internal recalibrations, it is possible to prevent changes in the measured values in long-term operation.