For the parasites incubated in 10 lg/ ml, the RM values of the PB-treated group decreasedat a more rapid rate than the PZQ-treated group. When incubated in 100 lg/ml all PB-treated flukes appeared immobile from 1 to 24 h when 91–100% died, while in the PZQ-treated group RM values were higher than that of PB and most flukes were still alive at 1–12 h, and at 24 h only 21% of flukes were killed.