Tritium release from lithium meta- and orthosilicate was studied inpile (LISA experiments) and out-of-pile. In addition to temperature, the dependence on neutron flux and purge gas flow rate, pressure and chemistry (additions of H2, O2 and moisture) were tested. Residence times for orthosilicate observed in LISA-2 are, above 500 °C, comparable with, but at 300 °C, several orders of magnitude larger than those of previous diffusion-controlled out-of-pile experiments. This discrepancy and the sensitivity on purge-gas chemistry indicate that surface effects dominate tritium release. From comparisons of experimental and theoretically predicted tritium release it is concluded that recombination of chemisorbed tritium is an important release process. In agreement with previous results it was found, that release from orthosilicate generally is faster than from metasilicate.