In 1982 and 1983, sheltered upper intertidal and supratidal habitats on Sylt island were quantitatively studied for platyhelminths. This included (1) monthy sampling of two accretion sites, one vegetated and the other bare, and two salt marsh sites, one grazed and the other ungrazed; (2) seasonal sampling of 4 transects across salt marsh areas and accretion zones; and (3) some 50 sites sampled once only. Each sample comprized (5-) 10 replicate cores of 2 or 5 cm² sampling area (depending on site). From these replicates, abundance of frequent species (n>10 individuals recorded, no juveniles) was calculated. Abundance unit is individuals per 10 cm² surface area (numerically equivalent to thousands per m²)