abstract the yields and compositions of volatile concentrates and essential oils obtained from compressed co2 extraction and hydrodistillation of a model herb, respectively, are compared. the experimental tests were undertaken on origanum vulgare l. ssp. virens (hoffm. et link) letswaart using both intact and communited bracts. the yields and compositions obtained from the communited bract sizes compared well for both extraction techniques. this is an indication that degradation of the oil during the distillation process was minimal. however, when the intact bracts were used, the compressed co2 extraction yield was significantly lower than that achieved by hydrodistillation. this stresses the need for an efficient pre-treatment step for the co2 extraction of volatile concentrates.