The lucanid beetle Ceruchus chrysomelinus Hochenwarth inhabits forests with a high density of moist red-rotten logs of both coniferous and deciduous trees. This habitat is very rare in Swedish forests of today and so is the species in itself. There are no recent records from the Swedish provinces of Skane, Halland, Vastergotland, Ostergotland and Halsingland, but new localities have recently been found on the island of Oland and in the provinces Sodermanland and Vastmanland. Palaeoentomological studies in southern Smaland indicate that the species was significantly more common 1 000 - 2 000 years ago than at present. In the few remaining large old-growth forests in northern and central Europe the species seems to be one of the most numerous wood beetle species, but it is probably dependent on a continuous supply of suitable logs at the landscape scale. At the majority of the present Swedish localities the number of suitable logs is low and the surrounding environments are unsuitable. Several sites with suitable habitat in the province of Uppland seem to be lacking the species, although populations exist only 1-2 km away. This could be explained by a low dispersal propensity. The largest populations now occur in Uppland at the lower part of River Dalalven and around Lake Vallen. During the last 25 years (1975-1999) Ceruchus chrysomelinus has been found on 10 localities outside of Uppland. We propose that the species can be used as an indicator species of forests with high conservation value.