Embedded in the ENVISAT validation programme of the chemistry instruments GOMOS, MIPAS, and SCIAMACHY, a large number of balloon-borne, aircraft and ground-based measurements were carried out in the years 2002 and 2003 at various locations. Unfortunately, by the date of the ACVE-2 conference, re-analyzed operational MIPAS data was almost only available for the year 2002 limiting the number of validation cases with the new operational version 4.61 (v4.61) data significantly. Generally, the MIPAS HNO3 profiles as processed with v4.61 are in good agreement with airborne observations in all cases with a good coincidence in time and space between the MIPAS observations and the correlative measurements. However, these validation cases have been confined so far to mid-latitudes only. Retrievals of MIPAS HNO3 profiles as obtained by different processors appear to be generally rather robust as proven by a statistics of inter-comparisons of HNO3 profiles between the operational v4.61 data and data processed with the IMK scientific processor. Ground-based correlative measurements based on the FTIR technique have been provided from different sites all over the world. Both column amounts and vertical profiles of HNO3 with coarse resolution can be derived from such measurements. This data is potentially very useful for monitoring the longer term quality of MIPAS satellite data. However, the comparison of those columns amounts and profiles is not straightforward and a careful and consistent procedure needs to be applied to determine comparable values for the columns as well as to take into account the different vertical resolutions of the space-borne limb emission and the ground-based solar absorption measurements. Further validation coincidences in different geophysical situations have to be considered based on v4.61 data before a final quantitative assessment on the quality of the MIPAS operational HNO3 data will become possible.