VIMOS is the Visible Multi-Object Spectrograph mounted at the Nasmyth
focus of the 8.2m Melipal (UT3) telescope of the ESO Very Large Telescope. VIMOS operates with four channels in three observing modes: imaging, multi-object spectroscopy (MOS), and integral field spectroscopy. VIMOS data are pipeline-processed and quality-checked by the Data Flow Operation group in Garching. The quality check is performed in two steps. The first one is a visual check of each pipeline product that allows the identification of any potential major data problem, such as, for example, a failure in the MOS mask insertion or an over/under exposure. The second step is performed in terms of Quality Control (QC) parameters, which are derived from both raw and processed data to monitor the instrument performance. The evolution in time of the QC parameters is recorded in a publically available database (http://www.eso.org/qc/). The VIMOS QC parameters include, for each of the four VIMOS channels, the bias level, read-out-noise, dark current, gain factor, flat-field and arc-lamps efficiencies, resolution and rms of dispersion, sky flat-field structure, image quality and photometric zeropoints. We describe here some examples of quality checks of VIMOS data.