  We point out the importance of two-body final states of weak isosinglet
neutral heavy leptons predicted in several models of new physics beyond the
standard model. We concentrate on muon-type neutral heavy leptons $L_\mu^0$
with mass $M<2$ GeV which can be searched for with increased sensitivity at a
new round of neutrino experiments at CERN and Fermilab. Providing explicit
decay rate formulae for the $e e \nu$, $e\mu \nu$, $\mu \mu \nu$, $\pi \mu$,
$\rho \mu$, and $a_1\mu$ final states, we use general scaling features to
estimate sensitivity of $L_\mu^0$ searches in current and future experiments,
emphasizing the importance of the $\pi \mu$ decay mode.
