Abstract. The IRI electron density topside has been constructed on the basis of the data available about thirty years ago. Recently a large amount of data from old topside sounders have been processed to get electron density profiles. These profiles allow to test IRI model under a wide spectrum of different conditions and to understand the behavior of the modeled topside. A set of 12 000 topside profiles have been chosen from the ISIS2 database, selecting those with the better quality of the inverted profile. An analysis of each IRI topside constitutive parameter has been done for all the experimental cases allowing to find some critical conditions under which the IRI topside could become completely unrealistic. In particular for very high solar activity at high latitudes it has been found that some IRI parameters could reach values that change drastically the shape of IRI topside. A proposal to control their range of variability is formulated in order to avoid the occurrence of such cases.