The human helminth parasite burdens on cyclorrhaphan flies was studied in an aboriginal settlement in Malaysia in 1987–88. Chrysomya megacephala (F.), which formed 79.5% of total fly population trapped in this settlement, had eggs of the roundworm Ascaris lumbricoides, the pinworm Trichuris trichiura and hookworm (Necator americanus and/or Ancylostoma duodenale) on the external body surface and gut lumen. There was a close correlation between monthly rainfall and the mean numbers of C. megacephala caught per two trap-hours. Eggs (but no larvae) of the parasites were found on flies when the monthly rainfall and the C. megacephala population were relatively high, in April-June 1987, October-November 1987 and March 1988. Human helminth eggs were also isolated from C. rufifacies (Macquart) and Hemipyrellia tagaliana (Bigot), being recorded from the latter in Malaysia for the first time.