To improve our understanding of factors influencing the success of natural regeneration with downy birch (Betula pubescens Ehrh.) and silver birch (Betula pendula Roth) on abandoned farmlands, a survey was conducted to analyse the effects of site conditions and site preparation characteristics. The study was based on a sample plot inventory conducted in one northern and one southern district of Sweden, in which 29 successfully established, naturally regenerated stands, about to be cleaned or thinned, were assessed. Radical site preparation increased stand density and uniformity of established regeneration, and gave faster initial development, than establishment without site preparation on former leys or meadows. Large proportions of the total sample area were classified as moist, and soils consisting of sand–fine sand or peat were frequent. The frequency of birch stems was highest in mesic sites, and on soils consisting of sand, sand–fine sand or peat. Distances to seed-trees were generally shorter than 80 m, and downy birch was the dominant species in most stands.