The distribution of Platyhelminthes was surveyed along two transects in tidal flats of the northeast coast of Queensland, Australia, in May 1990 and September 1991. Species numbers and densities as well as individual abundances and diversity increased from the high towards the low intertidal in relation to sediment composition. Along this gradient, platyhelminth assemblages of low intertidal sandflats, muddy sandflats and mudflats were distinguished with multivariate analyses. The distribution pattern was affected by the sediment parameter, and also by interactions with macrofauna. Sampling and analysis of the platyhelminth assemblage in tidal flats of Hinchinbrook Channel over time (November 1988 to October 1991) revealed annual and interannual variation, but no seasonality.