A reconnoitring profile from the ancient lagoon of Barsebäckmossen is described. The ingression of the sea probably occurred in connection with a transgression around the boundary between the Early and Late Atlantic periods. In the profile, a regression and a subsequent transgression are indicated during the earlier part of the Early Sub-Boreal period. In the central part of the ancient lagoon, another transgression during the later part of the Early Sub-Boreal period can be directly observed in the stratigraphy. The transgressions in Barsebäcksmossen agree well with the transgression scheme in Blekinge presented by Berglund (1964, 1971).