Tolerance to carbendazim, in Mycosphaerella fijiensis, the cause of black leaf streak in bananas, was found to be widespread in Western Samoa but was not found in Tonga or the Cook Islands. In laboratory tests, growth of M. fijiensis isolates from Western Samoa was inhibited by benomyl but only in three cases by carbendazim. Growth inhibition by benomyl in test plates was only temporary (3-4 days) after which the fungus grew normally. The use of tridemorph instead of benomyl is recommended for control of black leaf streak in Western Samoa. In Tonga and the Cook Islands the alternate use of benomyl with other fungicides is recommended to reduce the possibility of development of carbendazim tolerance in these countries.