Context: In the Treat Angina with Aggrastat and Determine Cost of Therapy with an Invasive or Conservative Strategy (TACTICS)-Thrombolysis in Myocardial Infarction (TIMI) 18 trial, patients with either unstable angina or non-ST-segment elevation myocardial infarction (UA/NSTEMI) treated with the platelet glycoprotein (Gp IIb/IIIa) inhibitor tirofiban had a significantly reduced rate of major cardiac events at 6 months with an early invasive vs a conservative strategy. Objective: To examine total 6-month costs and long-term cost-effectiveness of an invasive vs a conservative strategy. Design: Randomized controlled trial including a priori economic end points. Setting: Hospitalization for UA/NSTEMI with 6-month follow-up period. Patients: A total of 2220 patients with UA/NSTEMI; economic data from 1722 patients at US-non-VA hospitals. Intervention: Early invasive strategy with routine catheterization and revascularization as appropriate vs a conservative strategy with catheterization performed only for recurrent ischemia or a positive stress test. Main Outcome Measure: Total 6-month costs and incremental cost-effectiveness ratio. Results: The average initial hospitalization costs among those in the invasive strategy group were $15714 vs $14047 among those in the conservative stategy group, a difference of $1667 (95% confidence interval [CI], $387-3091). The in-hospital costs were offset significantly at the 6-month follow-up, with an average cost in the invasive group of $6098 vs $7180 in the conservative group, a difference of $1082 (95% CI, -$2051 to $76). The average total costs at 6 months, including productivity costs, for the invasive group was $21813 vs $21227 for the conservative group, a $586 difference (95% CI, -$1087 to $2486). The average 6-month costs excluding productivity costs in the invasive group was $19780 vs $19111 in the conservative group, a difference of $670, 95% CI; (-$1035 to $2321). Estimated cost per year of life gained for the invasive strategy, based on projected life expectancy, was $12 739 for the base case, and ranged from $8371 to $25769, based on model assumptions. Conclusions: In patients with UA/NSTEMI treated with the Gp IIb/IIIa inhibitor tirofiban, the clinical benefit of an early invasive strategy was achieved with a small increase in cost, yielding favorable projected estimates of cost per year of life gained. These results support the broader use of an early invasive strategy in these patients.