  We present far-IR ISO observations of three early-type galaxies in the Virgo
cluster. The data were recorded using the ISOPHOT instrument in both the P32
oversampled maps and the P39/37 sparse maps. The maps reach the limiting
sensitivity of the ISOPHOT instrument at 60, 90, and 180$\mu$m. Two of the most
prominent elliptical galaxies in Virgo -- NGC 4472 and NGC 4649 -- clearly show
no emission at far-IR wavelengths at a level of few tens of mJy, but NGC 4636
is detected at all three wavelengths. We have computed the far-IR emission from
dust for NGC4472 and NGC4636 under the assumption that dusty outflows from
evolving red giant stars are continuously supplying dust to the interstellar
medium and that the grains, once diffused into the interstellar medium, are
sputtered away by collisions with ions. While the calculated fluxes are
consistent with the observed upper limits for NGC4472, the dust emission
detected in NGC4636 support the hypothesis that additional dust has been
accreted in a very recent ($\lta$ few $10^8$ yrs) merger with a dusty, gas-rich
galaxy.
