CONTEXT: Few data exist about the long-term outcomes of patients with Lyme disease. OBJECTIVE: To assess the long-term outcomes of patients with Lyme disease. DESIGN: Two-part project including a community-based longitudinal cohort study and a matched cohort study. SETTING AND PARTICIPANTS: Six hundred seventy-eight patients identified from a random sample of all reports of Connecticut residents with suspected Lyme disease submitted to the Connecticut Department of Public Health from 1984-1991 were evaluated in the longitudinal study; for a random subsample of 212 patients from the larger study, 212 age-matched controls without Lyme disease also were enrolled. MAIN OUTCOME MEASURES: Self-reports or parents' reports of symptoms and ability to perform certain daily activities since diagnosis of Lyme disease; scores on the 36-Item Short-Form Health Survey and the Center for Epidemiologic Studies-Depression scale, for adults, by case-definition status and between patients and controls. RESULTS: Of the 678 patients, 51.6% were female, 34.4% were children, and 64.3% met the national surveillance case definition for Lyme disease. Most patients (85.6%) were treated with antimicrobial agents. Interviews were conducted a median of 51 months after diagnosis (range, 15-135 months). An increased frequency of symptoms (eg, pain, fatigue) or of difficulty with daily activities (eg, performing housework, exercising) was reported by 69% of the patients, although few (19%) of these problems were attributed to Lyme disease. Whenever there was a statistically significant difference in the frequencies of either increased symptoms or increased difficulties with typical activities between those who did or did not meet the surveillance case definition, in all instances the greater frequency of problems was in the group that did not meet the case definition. The frequencies of reports of both increased symptoms and increased difficulties with typical activities among patients who had been diagnosed as having Lyme disease were similar to those among age-matched controls without Lyme disease. CONCLUSIONS: In this cohort, although many patients reported increases in symptoms and/or increased difficulties with typical daily activities between 1 and 11 years after diagnosis of Lyme disease, the frequencies of these reports were similar to the frequencies of such reports among age-matched controls without Lyme disease.