The validation of cloud microphysical properties derived from satellite data with in situ observations is generally difficult due to the spatial and temporal variability of observed clouds. Two missions during SUCCESS concentrated on orographic wave clouds that exhibited relative spatial and temporal homogeneity. A comparison has been made of effective ice particle diameters derived from multi-spectral satellite data with in situ measurements from the MASP and PVM instruments aboard the DC-8 aircraft. For both days, the satellite-derived effective diameters fall well within the bounds of the in situ data. ¿ 1998 American Geophysical Union