Previous studies on animals have revealed that garlic (Allium sativum) is effective in reducing blood and tissue lead concentrations. The aim of this study was to investigate therapeutic effects of garlic and compare it with D-penicillamine in patients with chronic lead poisoning. After coordination and obtaining informed consent, clinical examinations and blood lead concentration (BLC) of 117 workers at a car battery industry were investigated. BLC was determined by heated graphite atomization technique of an atomic absorption spectrometer. The workers were randomly assigned into two groups of garlic (1200 lg allicin, three times daily) and D-penicillamine (250 mg, three times daily) and treated for 4 weeks. BLC was determined again 10 days post-treatment. Clinical signs and symptoms of lead poisoning were also investigated and compared with the initial findings. Clinical improvement was significant in a number of clinical manifestations including irritability (p = 0.031), headache (p = 0.028), decreased deep tendon reflex (p = 0.019) and mean systolic blood pressure (0.021) after treatment with garlic, but not D-penicillamine. BLCs were reduced significantly (p = 0.002 and p = 0.025) from 426.32 € 185.128 to 347.34 € 121.056 lg ⁄ L and from 417. 47 € 192.54 to 315.76 € 140.00 lg ⁄ L in the garlic and D-penicillamine groups, respectively, with no significant difference (p = 0.892) between the two groups. The frequency of side effects was significantly (p = 0.023) higher in D-penicillamine than in the garlic group. Thus, garlic seems safer clinically and as effective as D-penicillamine. Therefore, garlic can be recommended for the treatment of mild-to-moderate lead poisoning.