In a data sample of 78.3 pb(-1) collected in 1996 and 1997 by the ALEPH det
ector at centre-of-mass energies from 161 to 184 GeV, invisible decays of a
Higgs boson have been searched for in the reaction e(+)e(-) --> hZ, where
the Z can decay into e(+)e(-), mu(+) mu(-) or <q(q)over bar>. No evidence f
or a signal is found and limits on the production cross section are derived
as a function of the Higgs boson mass. These results are combined with tho
se obtained in an update of the analyses of the ALEPH data taken at LEP 1.
For a production cross section equal to that of the minimal standard model
Higgs boson, masses below 80 GeV/c(2) are excluded at 95% C.L. (C) 1999 Els
evier Science B.V. All rights reserved.