The incidence and the temporal pattern of tick bites were studied in a population frequently out-of-doors in a tick endemic area in south-eastern Sweden between May 2000-March 2001. The participants, who were well aware of tick-borne diseases, inspected their skin daily from May until September and completed a diary sheet, registering visited geographical places, time out-of-doors, observed tick-bites, etc. The participants were also given questionnaires in both the initial and final stages of the study, asking questions about their earlier history of tick-bites, previous tick-borne diseases and out-of-door activities. The incidence was 0.04 (95% confidence interval 0.02-0.06) tick-bitten participants/10 h spent out-of-doors. In total, the participants registered 1767 tick bites, i.e. an incidence of 0.14 (95% CI 0.10-0.18) tick-bites/10 h spent out-of-doors. Within 6 months after the registration period, 8/235 (3%) had been treated for physician-diagnosed Lyme borreliosis. In conclusion, this study found a 4% risk to be tick-bitten per 10 h spent out-of-doors. The risk of contracting Lyme borreliosis was 1/221 tick bites (0.5%, 95% CI 0.44-0.56). Thus, our results indicate a low risk of acquiring Lyme borreliosis when using daily tick checks and we underline the opinion of not recommending routine prophylactic treatment for observed tick-bites.