BACKGROUND: The accuracy of ectopic pregnancy rates based on nationally representative data has been compromised for many years, impairing surveillance and evaluation of the continued public health importance of this condition. PURPOSE: To estimate long-term population-based ectopic pregnancy rates and trends within a defined population over a largely unevaluated time period, including the evaluation of trends in outpatient versus inpatient management and medical versus surgical treatment modalities. METHODS: Using computerized Group Health Cooperative inpatient and outpatient data, age-adjusted and age-specific ectopic pregnancy rates were calculated from 1993 to 2007 among enrollees aged 15-44 years. Overall trends and trends for care setting (inpatient versus outpatient) and treatment modality (medical versus surgical) were also evaluated. Analyses were conducted in 2009. RESULTS: Between 1993 and 2007, a total of 2114 ectopic pregnancy cases (726 inpatient; 1388 outpatient) were identified among 1,180,070 woman-years, an annual age-adjusted ectopic pregnancy rate of 17.9 per 10,000 woman-years. Rates were stable from 1993 to 2004 and increased in the most recent 3 years (2005-2007, rate=21.1 per 10,000 woman-years). Rates per 1000 pregnancies increased over the 15-year period from 19.2 to 26.2 per 1000 pregnancies (p-value=0.001). Inpatient-diagnosed cases decreased from 45.4% in 1993-1995 to 26.9% in 2005-2007 (p-value<0.0001) and the percentage with surgical treatment decreased from 48.1% to 30.7% (p-value<0.0001). CONCLUSIONS: The results suggest a trend toward increasing ectopic pregnancy rates over a recent 15-year period. Rates are similar to the last available national estimate, suggesting that the significance of ectopic pregnancy as a public health problem has not diminished in these intervening years.