INTRODUCTION AND PURPOSE Lyme borreliosis is in Sweden the most common vector-borne disease with approximately 10.000 individuals affected each year. Previous studies have suggested that conscripts compose a population of high risk to tick-bites and others have linked tick attachment to different body odour. In several countries the peasant population have observed that garlic keep the cattle free from ticks. The purpose of this study was to determine if Swedish conscripts are a population of high risk to tick-bites and thereby tick-borne diseases and to study if tick-bites can be prevented by garlic consumption. METHODS The survey participants, n=100 (50 in each group) consumed garlic / placebo for eight weeks, had a wash-out period, then changed to placebo / garlic consumption for another ten weeks. The study drug contained 1200 mg Allium sativum, administrated 600 mg twice daily. During the study period the conscripts performed a daily inspection of their skin and filled in a diary-sheet. Questionnaires including questions on e.g. smoking habits, other medication, adverse events and tick-borne disease manifestations were answered when; entering the study, before and after the wash-out period and at the end of the study. RESULTS The total amount of registered tick-bites during the study period was 286. On average the participants registered 0.2 bites per week during military service compared to 0.03 bites per week during leave. Two of the participants developed an erythema migrans. When consuming garlic, results show a significant reduction in tick-bites, included and excluded a participant who reported 86 tick-bites on one occasion, compared to consuming placebo. Also, the incidence was lower when taking account the reported number of bitten participants both in intention to treat and per protocol. CONCLUSIONS Swedish marine conscripts are a population of high risk to tick-bites during their military service and preventive measures including vaccinations against diseases transmitted by ticks should be considered. Garlic had a preventive effect against tick-bites, however significantly differences were not seen in intention to treat calculations and more studies are needed.