The present occurrence and vitality of Lobaria scrobiculata (Scop.) DC. were investigated at 67 localities (50 old and 17 new) in southern Sweden. Before 1950 L. scrobiculata was found at more than 300 localities in southern Sweden. However, it was only confirmed at two out of 50 thoroughly investigated old localities. An investigation of recently found localities (new) and confirmed ‘old’ sites showed that there have been decreases in population size, thallus size, fertility, number of phorophytes, and cliff colonization. In southern Sweden today L. scrobiculata is confined to old deciduous trees in regions with comparatively low air pollution and a high relative humidity. Apothecia have not been found in southern Sweden since 1947, although in the past, fertile material was collected from 35 localities in this region. The author suggests that this species, like many other lichens with the cyanobacterium Nostoc as photobiont, is currently more endangered by air pollution than by any other human activity and that it is seriously endangered in the southern part of Sweden.