Dextran hydrogels were formed in situ by enzymatic crosslinking of dextran-tyramine conjugates and their mechanical, swelling and degradation properties were evaluated. Two types of dextran-tyramine conjugates (M n,dextran ¼ 14 k, M w /M n ¼ 1.45), i.e. dextran-tyramine linked by a urethane bond (denoted as Dex-TA) or by an ester-containing diglycolic group (denoted as Dex-DG-TA), with different degrees of substitution (DS) were prepared. Hydrogels were rapidly formed under physiological conditions from Dex-TA DS 10 or 15 and Dex-DG-TA DS 10 at or above a concentration of 2.5 wt% in the presence of H 2 O 2 and horseradish peroxidase (HRP). The gelation time ranged from 5 s to 9 min depending on the polymer concentration and HRP/TA and H 2 O 2 /TA ratios. Rheological analysis showed that these hydrogels are highly elastic. The storage modulus (G 0 ), which varied from 3 to 41 kPa, increased with increasing polymer concentration, increasing HRP/TA ratio and decreasing H 2 O 2 /TA ratio. The swelling/degradation studies showed that under physiological conditions, Dex-TA hydrogels are rather stable with less than 25% loss of gel weight in 5 months, whereas Dex-DG-TA hydrogels are completely degraded within 4-10 d. These results demonstrate that enzymatic crosslinking is an efficient way to obtain fast in situ formation of hydrogels. These dextran-based hydrogels are promising for use as injectable systems for biomedical applications including tissue engineering and protein delivery.