In a field experiment, the accumulation of trematode (Echinostomatidae) metacercariae by the New Zealand cockle Austrovenus stutchburyi was compared among treatments with different seabed hydrodynamics and sedimentation rates. There was no significant difference among the treatments in the rate at which cockles accumulated metacercariae, suggesting that infection rates are not influenced by water flow conditions within the normal range experienced in natural habitats. There was, however, substantial spatial variation in infection rates among the experimental plots. This result indicates that metacercarial accumulation varies horizontally as well as vertically within the intertidal zone.