The behaviour and survival of captive-born least weasels Mustela nivalis nivalis released in nature were reported in this study. Altogether 27 captive-born and six wild-caught weasels were equipped with radio transmitters and their survival was studied as a function of age and season. The daily mortality rate was generally higher in captive-born than in wild-caught weasels. The survival of captive-born weasels was highest if they were released during the summer and hence when they were young. Differences in the behavioural patterns of captive-born and wild-caught weasels were apparent. Captive-born weasels were often more visible in the field and were less timid than wild-caught weasels. Results suggest that to be successful, restocking of weasels should be done with young animals, which are preferably released during the season with abundant food resources.