From 1999 to 2003, 83 captive-reared Capercaillies were fitted with transmitters, released in the Harz Mountains region, and subsequently tracked by radio telemetry. The purpose was to achieve an effective record of survival chances, spacing, habitat use and feeding habits of the released birds, in order to evaluate the success of the project and to improve measures for future reintroduction projects. Some 23% (n = 18) of the radio-marked birds survived until either the transmitter or contact was lost. The median survival duration was 13 days, whereby hens (18 days) survived longer than cocks (12 days). The highest losses (79%, n = 48) occurred within the first four weeks after release. Of 61 deaths recorded, 62% were victims of foxes, 10% were killed by Goshawks, and 7% by Lynxes. In addition to mortalities where cause of death was unclear, individual birds were killed by traffic, dogs or died of under-nourishment. The main causes of the high mortality rate can be sought in the physiological and ethological deficits, which result from rearing in captivity. These include in particular a lack of predator-experience, and a probable inability to adjust adequately to food sources in the wild. Additionally, 5% of the losses were related to predators attracted to the area of the acclimatization pen. The released birds had activity ranges ("search areas") from less than 1 ha to up to 17.000 ha, whereby the majority of activity ranges (77%) comprised up to 1.000 ha. The recorded size of the activity range, as well as the maximum distance from the release site, increased with the length of the location period. The wide-ranging dispersal of the released birds in some cases was not only due to the generally marked dispersion of the juvenile Capercaillies, but possibly also to the unsuitability of the habitat at the release sites. Within the activity ranges birds established smaller centres of activity, which they frequented until at least death, or loss of the transmitter. The size of the activity centres (n = 17) varied between 0.5 and 327 ha. In 70% of all cases, the birds covered a daily distance of not more than 500 m. Some 67% of all locations fell within a radius of 3 km from the release site. The greatest distances recorded were up to a maximum of 22 km (♀). Arising from project experience, release direct from transport boxes is recommended. This helps to avoid additional losses at the acclimatization pen, and the release site can be selected more flexibly. Other improvement measures in the rearing and release methods are essential (e.g. early intensified diet provision appropriate to the species, training programmes, adequate disease prophylaxis), without which further releases of captive-reared grouse into the wild can no longer be justified.