The tissue locations and effects produced by metacercariae of Diplostomum (Austrodiplostomum) mordax and Tylodelphys destructor in the brain of 30 silversides (Basilichthys australis) from Lake Riñihue in Chile, were evaluated. Metacercariae were mainly observed in the interlobular infoldings, meninges and ventricles of the brain. The prevalence was 18 (60%) and the intensities were usually low (1 to 9 metacercariae), with no inflammation or invasion of the parenchyma, except for one fish which had 130 parasites associated with a moderate inflammatory reaction. Asymmetry in the distribution of metacercariae in the cerebral hemispheres was observed in one (3%) of the 30 fish.