The efficacy of the drugs currently available for treatment of infection with Trichuris trichiura is low compared with that of the drugs used against roundworm and hookworm. Single-dose combinations of albendazole with ivermectin or of albendazole with diethylcarbamazine (DEC) have recently been seen to produce raid and sustained reductions in Wuchereria bancrofti microfilaraemia. This observation prompted the present study, on the efficacy of these combinations against trichuriasis. The drug regimens tested were albendazole (400 mg) alone, albendazole (400 mg) with ivermectin (200 micrograms/kg), and albendazole (400 mg) with DEC (6 mg/kg). Most (155) of the 176 children (4-14 years of age) who each provided a single, pre-treatment, stool sample were found positive for Trichuris ova. These 155 were each randomly allocated to one of the three treatment groups and checked for infection 3 weeks post-treatment, again by a single stool examination. Single-dose therapy with albendazole plus ivermectin produced a 'cure rate' (79.3%) and an egg-reduction rate (93.8%) which were significantly higher than the corresponding rates produced by albendazole alone or albendazole plus DEC (P < 0.01 for each). The efficacies of albendazole with DEC and of albendazole alone were statistically equivalent. Single-dose treatment with the albendazole-ivermectin combination appears to be highly effective against trichuriasis and could prove valuable for routine use.