The majority of sixteen type 3 ordinary chondrites studied contain D/H ratios above the typical terrestrial range. We observe the most extreme deuterium enrichments in the least metamorphosed samples, and a trend of decreasing D/H with increasing metamorphism as measured by thermoluminescence sensitivity. Stepwise pyrolysis of bulk meteorite samples demonstrates that the amount of water released decreases rapidly with increasing temperature, and that the 450 ¿C--750 ¿C heating step released the most deuterium enriched water. More detailed stepwise pyrolysis of one of the least metamorphosed ordinary chondrites, Semarkona, produces water from the 550 ¿C--650 ¿C heating step which has a ΔD of +5740%0 (SMOW). Although this is the most deuterium-rich composition yet encountered in a solar system material, it may not represent a limiting value. It is suggested that a deuterium enrichment of this magnitude may only be produced by ion-molecule reactions in interstellar clouds.