High spatial resolution integrated water vapor (IWV) estimates are available from the MERIS spectrometer on board of Envisat. Unfortunately cloud cover results in loss of a large amount of MERIS IWV pixels. Here methods are presented for filling cloud gaps in MERIS IWV scenes, first, by directly interpolating remaining pixels not affected by clouds, and second, by fusion with cloud insensitive IWV observations from ground stations of the GPS network. Results are validated by independent IWV estimates obtained from suited SAR interferograms. The results indicate that the procedure works mathematically in a correct way, but that the physical application of the results is strongly hampered by MERIS pixels affected by not automatically detected clouds.