To determine the therapeutic usefulness of benzimidazoles in trichinellosis, 117 patients from a single outbreak were treated either with albendazole alone (N = 59) or with a regimen including tiabendazole followed by flubendazole (N = 58). The criteria of disease activity were evaluated at days 1, 7, 15, and 45. No difference was found between the two groups with regard to the evolution of myalgia, fever, fatigue, new clinical manifestations, or laboratory and serologic data. Both treatment regimens were well tolerated. In all, 30 patients of the albendazole group and 29 of the tiabendazole-flubendazole group were reevaluated 16 months later. Serology was negative in 70% of the albendazole-treated patients vs 34.5% of the tiabendazole-flubendazole-treated patients (P less than 0.01). The muscle biopsy examination of nine patients suggested less parasitic infection in the albendazole group. In conclusion, no difference was noted during the early therapeutic responses to the drugs used, but albendazole might be more effective than the other regimen in treating residual larval infestation estimated 16 months after the onset of the disease.