Neutralact(R), the DSM brand name of a lactase enzyme preparation, obtained from a homologous rDNA strain of Kluyveromyces lactis, was subjected to a series of toxicological tests to document the safety for use as a processing aid in the dairy industry. The enzyme preparation was examined for subacute oral toxicity and mutagenic potential. As a result of these tests, no evidence of oral toxicity, mutagenicity or clastogenicity was found. Administration of the lactase enzyme preparation at doses of 500, 3000 and 10,000 mg/kg body weight/day for 28 days did not induce noticeable signs of toxicity. The no-observed-adverse-effect level (NOAEL) of the enzyme preparation in the acute toxicity study was 10,000 mg/kg body weight/day (equivalent to 114,000 NL units/kg body weight/day). It can be concluded that no safety concerns were identified in the studies conducted with this lactase enzyme preparation derived from Kluyveromyces lactis under controlled fermentation conditions.