An enzyme preparation containing glucanase produced by the fungus Trichoderma harzianum is intended to be used to improve the clarification and filtration of wines. The safety of a glucanase preparation was assessed in a series of toxicological tests to document its safety in use. Oral administration to rats of up to 10mL/kgbw/day (equivalent to a total organic solids dosage of 1258mg/kgbw/day or a glucanase dosage of 1882 BGXU/kgbw/day) for 13 weeks did not cause any adverse effect. The test substance was not found to be mutagenic in the bacterial reverse mutation assay, nor did it cause chromosomal aberrations in cultured human lymphocytes. The safety margin for exposure is estimated to be in the range of 2100–72,000 depending on the estimate for daily wine consumption. The results of these studies demonstrate that an enzyme preparation containing glucanase may be considered safe when employed in wine processing.