A search for invisible decay of Higgs bosons produced in the
Higgsstrahlung process in e+e- collisions at LEP is performed using data
taken by the OPAL detector at centre of mass energies between 183 and
209 GeV. The analysisis motivated by models predicting the decay of the
Higgs boson into a pair of stable weakly interacting neutral particles,
such as the lightest neutralino in the Minimal Supersymmetric Standard
Model. The same selection is applied to search for nearly invisible
decays of the Higgs boson resulting from a cascade decay to a stable
weakly interacting neutral particle, H -> X Y -> X X Z*. No excess of
events over the expected background from Standard Model processes is
observed. Limits on the production cross-section of invisibly decaying
Higgs bosons produced in association with a Z boson are derived.
Assuming a branching ratio BR(H -> invisible) = 1, a lower bound on the
Higgs boson mass is placed at the 95% confidence level. Limits on the
production of nearly invisibly decaying Higgs bosons are also given.