AIM: To compare the efficacy and safety of five days apostrophe therapy of mebendazole (MBZ) versus quinacrine (QC) on human giardiasis in children.METHODS: A clinical trial was carried out in paediatric patients (aged 5-15 years) with confirmed symptomatic G. duodenalis mono-infection. Patients were randomly assigned to receive either MBZ [200 mg taken three times per day (TID) (n = 61)] or QC [2 mg/kg bodyweight tid (n= 61)], both for five days. Follow-up faecal samples were obtained at 3, 5 and 7 d after the end of the treatment.RESULTS: Although the frequency of cure was higher for QC (83.6%) than for MBZ (78.7%), the difference was not statistically significant (P ＞ 0.05). Adverse events were reported more in the QC group (P ＜ 0.05),all of them transient and self-limiting.CONCLUSION: Despite final cure rates ocurring lower than expected, the overall results of this study reconfirmed the efficacy of MBZ in giardiasis and also indicate that, although comparable to QC, at least in this setting the 5 d course of MBZ did not appear to improve the cure rates in this intestinal parasitic infection.