  After reviewing the multifrequency behaviour of the Isolated Neutron Stars
detected so far, we analyze for each object the efficiency of conversion of the
star's rotational energy loss into optical, X and gamma radiation. Although the
number of pulsars detected at different wavelengths is rather limited, a
pattern is seen to emerge from our analysis pointing towards the period
derivative as the leading parameter to describe the multifrequency emission of
INS. One object in particular, PSR 1509-58, stands out as archetypal for the
Pdot-dependence of its luminosity at different wavelengths.
