The behavior of dextransucrase from Leuconostoc mesenteroides NRRL-B-512F in the presence of organic solvents was investigated. The activity and stability of this enzyme were studied in the presence of various concentrations (% v/v) of dimethysulfoxide (DMSO), dimethylformamide (DMF), ethanol, acetone and acetonitrile. The stability was measured at 4°C and 30°C. Generally the initial velocity of dextransucrase decreases proportionally to solvent concentrations except in water–DMSO mixture. Indeed in 25% DMSO (v/v), 45% of the activity in pure water was detected whereas 26% was measured in 10% DMSO (v/v). Moreover the loss of activity is much more considerable in the presence of acetonitrile than in the presence of other solvents. In 20% acetonitrile (v/v), only 11% of the activity was measured. Concerning the stability of the enzyme it appears that it is more stable at 4°C than at 30°C. Surprisingly dextransucrase is more active after a period of contact with some solvents, especially DMSO or ethanol, than in acetate buffer. After 2 days in 20% DMSO (v/v) at 4°C, 300% of the initial activity remained and 250% at 30°C. This increase of activity is also observable after 2 days in 20% ethanol (v/v) where 180% of the initial activity is measured.