The authors discuss the results of a double-blind, placebo-controlled, randomised study on the efficacy of mebendazole versus placebo in the treatment of human toxocariasis in 45 and 43 patients respectively, who exhibited evocative clinical and biological symptoms and a seropositivity. Scores were used to quantify clinical (20 parameters) and biological (blood count, sedimentation rate, determination of total and anti-Toxocara IgE, serodiagnosis by immunoelectrophoresis) abnormalities. The reassessment were done 1 month after the end of treatment. Analyzing the results showed a similar efficacy of mebendazole and placebo on the score of clinical signs; the score of biological abnormalities was significantly reduced in mebendazole group, but the serodiagnosis by immunoelectrophoresis was the only parameter that was significantly normalized. These results corroborate previous prospective studies and allow to make a conclusion in favour of a moderate efficacy of mebendazole.