Objective: To assess the effectiveness of garlicin preventing infection of acute myelogenous leukemiapatients during chemotherapy and the side effect ofgarlic. Design: A randomized placebo-controlled clinicaltrial. Setting: First General Hospital of West ChinaUniversity of Medical Sciences, a tertiary carehospital. Patients: Thirty-eight consecutive acutemyelogenous leukemia patients diagnosed by clinicalpathological evidence without infection or takingantibiotics on admission, were stratified into 3strata. according to whether they were newly diagnosed,relapsed or in postremission consolidation. Within eachstratum, patients were randomly assigned into thetreatment (trt grp, n=19) or control (ctrl grp, n=l9). Intervention: Patients in trt grp were treated by10 ml of aqueous garlic extract (AGE), equivalent to 10grams of raw garlic, 3 times a day, from the start ofchemotherapy till their peripheral white blood cellcount exceeded 2 x 10('9)/L or till 28 days. Patients inthe ctrl grp were given normal saline, according to thesame dosage and schedule. Patients in both groupsreceived the same standard chemotherapy regimen. Whenpatients had fever and infection was suspectedantibiotics were given and guided by the detailedguidelines for antibiotics. Results: There was no significant differencebetween the 2 groups in the incidence of inectiondefined as fever plus microbiologically or clinicallydocumented infection and fever when the peripheralneutrophil count was less than 0.5 x 10('9)/L. However,patients in the trt grp had significantly less fungalcolonization than patients in ctrl grp (1.21(+,-)1.31 fortrt grp and 2.32 (+,-) 1.38 for ctrl grp, p=0.0156,two-sample Wilcoxon rank-sum test). This decreasednumber of fungal colonization was not associated with adecreased fungal infection. Conclusion: Compared to placebo, garlic did notdecrease the total febrile episodes but it could lowerthe number of fungal colonization. Further studies onthe effectiveness of garlic in preventing infectionespecially fungal infection of neutropenic patients are warrented.