['To determine if the early antibiotic treatment of deer tick bites prevented Lyme disease.', 'Prospective, double-blind, placebo-controlled, antibiotic treatment.', 'Private practice in an area endemic for Lyme disease.', 'Patients between 3 and 19 years of age who received antibiotic treatment within 3 days following a deer tick bite.', 'Patients received an antibiotic or placebo and were followed up for stage I and II disease. All patients had blood drawn at the time of presentation and 6 weeks later for immunofluorescent antibodies (IFA).', 'One patient in the placebo group developed clinical Lyme disease associated with an IFA titer of 1:32, considered weakly positive. Three other patients in the placebo group developed an IFA titer of 1:32; one had an influenzalike illness and two had no symptoms. None of the study patients developed any neurologic, cardiac, or arthritic symptoms in the 1- to 3-year follow-up.'] Does the value of early treatment of deer tick bite for the prevention of Lyme disease?