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The goal of this study is to identify risk factors for developing Lyme disease in Chester County, Pennsylvania. For this analysis, factors associated with outdoor activities will be investigated to determine if they increase or decrease risk. A telephone questionnaire was used to conduct a retrospective cohort study on a group of Chester County residents that were previously part of a case-control study conducted in 1998. There were 186 respondents; 93 cases and 93 controls from the previous study participated. Variables that were significant (p<0.2) were considered for the multivariate model. These were: performing yard work, visiting parks, walking or jogging, playing outdoor games attended fields, taking care of horses, picnicking in the yard, wearing light colored clothing, and checking for ticks while participating in outdoor activity. A stepwise logistic regression was performed to create the most parsimonious model. For this multivariate model, the included variables were frequenting parks, walking or jogging, picnicking in the yard and wearing light colored clothing. The goodness-of-fit test showed that there is no significant difference between the estimates generated by the model and the data which supports the model. This study shows that picnicking in the yard and wearing light colored clothing are risk factors while frequenting parks and walking or jogging appear to be protective.