  We present the results of second epoch simultaneous multifrequency
observations of 45 sources out of the 55 in the sample of High Frequency
Peakers (HFP) by Dallacasa et al. (2000). Seven of the stellar sources (i.e.
16% of the total number of sources and 26% of the stellar fraction) no longer
show a convex spectrum and are thus likely to be flat spectrum quasars in an
outburst phase during the first epoch of observations. The rest frame peak
frequency distribution of HFP quasars extends up to ~45 GHz while that of HFP
galaxies is confined to $\le 17$ GHz. Imaging at 1.465 GHz and 1.665 GHz has
revealed extended emission for 31% of sources, a substantially larger fraction
than found for GPS sources (~10%). In the case of HFP quasars, but not of HFP
galaxies, extended emission is associated with strong variability, consistent
with a core-jet structure.
