  The production of invisible pairs of lightest neutralinos accompanied by a
large-angle hard photon in the reaction $e^+ e^- \to \chi^0_1 \chi^0_1 \gamma$
is studied at LEP2 energies. The most general gaugino/higgsino composition of
the $\chi^0_1$ within the Minimal Supersymmetric Standard Model is assumed. The
spectrum of the observed photon is derived within the framework of the
$p_t$-dependent structure-function approach, whose accuracy is assessed to be
within the foreseen experimental accuracy at LEP2. Higher-order QED corrections
due to undetected initial-state radiation are also included. A comparison with
the Standard Model main background from $e^+ e^- \to \nu \bar \nu \gamma$ is
performed for optimized photon kinematical cuts. Quantitative conclusions on
the signal/background ratio are given for a wide range of values of the SUSY
parameters.
