A truncated xylanase gene from the ruminal bacterium Fibrobacter succinogenes S85 was expressed in Chinese hamster ovary (CHO) cells and pancreatic acinar 266-6 cells using the SV40 early promoter and the mouse Amy-2.2 promoter/enhancer, respectively. The enzyme produced in both systems was active and secreted into the medium. The xylanase secreted from CHO cells was highly glycosylated and became sensitive to protease digestion compared to the unglycosylated form.