Summary Seed moisture content may significantly affect the storage life of both agricultural and forest species. Seed store managers therefore need an easy and reliable method for routinely checking moisture contents. A robust, portable, easy- to-use electrical seed moisture meter, the Protimeter Grainmini V, was evaluated on samples of Eucalyptus globulus, E. pulchella and E. obliqua seed. Meter readings were well correlated with gravimetric moisture contents ranging from 4.7% to 24.3% of oven dry weight. Relative humidity readings were also made on the equilibrium atmosphere within sealed bags of seed to see whether it might be feasible to derive seed moisture indirectly via relative humidity. For E. globulus, the fertile seed had gravimetric moisture contents several percent lower than the associated chaff, which normally comprises the bulk of a stored Eucalyptus seed lot. Equations were derived to define the relationship between the overall moisture content and that of the fertile seed, and the way this relationship is affected by the fertile seed/chaff ratio. Fertile seed also gave a higher meter reading than chaff at the same gravimetric moisture content. These effects were much less marked with smaller-seeded eucalypts. These findings have been incorporated in calibration tables for the electrical meter, which is now used by Forestry Tasmania to screen all Eucalyptus seed prior to and during storage. Results should be generally accurate to within about ± 1 % of oven dry weight. The concept of deriving seed moisture content indirectly through the equilibrium humidity of the seed atmosphere seems sound in principle but is impractical for this purpose at its present stage of development.