The objective of this study was to examine the pattern of emergency department (ED) utilization among a cohort of ED users over a 3-year period and to identify factors predicting use. Billing records were used to track one hospital's cohort of adult frequent ED users (> or = 3 visits/per year) over a 3-year period. Frequent and (< 3 visits/per year) infrequent users were compared by age, gender, marital status, insurance status, and hospitalization rates. We compared the number of ED visits by patients in the two groups during follow-up years. Logistic regression analyses were performed to identify factors predicting ED visits by patients in the two groups in the follow-up years. Results from the study showed that frequent users were younger (P < 0.01) and more likely to be male (P < .01). Patients identified as frequent users in the first year were 52 to 77% more likely to visit frequently in the following two years. Logistic regression analysis showed the pattern of prior ED use was the best predictor of future use. Other factors (including age, gender, marital status, insurance status, and hospitalization following an ED visit) were not significant independent predictors of frequent ED use. Our data revealed that the past history of frequent ED use is predictive of future frequent ED use. Studies are needed on effective interventions to determine the reasons for continued frequent ED use.