  Proton acceleration in nearby blazars can be diagnosed measuring their
intense TeV $\gamma$-ray emission. Flux predictions for 1101+384 (Mrk421) and
1219+285 (ON231), both strong EGRET sources (0.1-10 GeV), are obtained from
model spectra of unsaturated synchrotron pair cascades fitted to publicly
available multifrequency data. An experimental effort to confirm the predicted
emission in the range 1-10 TeV would be of great importance for the problems of
the origin of cosmic rays, the era of galaxy formation and the cosmological
distance scale.
