OBJECTIVES: Revascularization procedures are often carried out during hospitalizations for acute coronary syndrome (ACS). Our objectives are to estimate the costs during the first year of follow-up after initial (index) hospitalization for ACS stratified by whether or not revascularization took place at this hospitalization. METHODS: This consisted of Kaiser Permanente Medical Care Program Nothern California patients age > 40 years, and hospitalized with ACS during January 1, 1999 to December 31, 2000, and without ACS hospitalization during 6 months prior. Costs expressed are those incurred by the health plan. RESULTS: A total of 14,852 patients met inclusion criteria. Mean age was 67.2 years; 63.9% were male. The distribution of revascularization during index hospitalization was 2457 CABG (16.5%), 3257 PCI (21.9%), and 9138 no procedure (61.5%). Index total hospitalization costs were: CABG ($34,307 + 26,515), PCI ($14,863 + $11,665), no procedure ($11,059 + 16,497). One-year follow-up costs were highest for no procedure [$17,669 + 32,510 ($7,781 median)], intermediate for CABG [$12,763 + 22,676 ($5,670)] lowest for PCI [$12,297 + 22,197 ($4,336)]. Percent of total costs by type of resource used (clinic, hospital, pharmacy, respectively) were for CABG 36.5%, 45.3%, 9.2%, for PCI 30.1%, 57.5%, 10.4%, and for no procedure 24.3%, 62.6%, and 7.5%. As expected, follow-up costs were considerably impacted by whether or not revascularization was performed. One-year revascularization rates were 15.0% for the PCI group, 14.3% for no procedure, and only 2.2% for CABG. One-year mean follow-up costs with and without revascularization were: CABG ($28,867 with and $12,401 without revascularization), PCI ($34,673 with and $8,344 without revascularization), no procedure ($39,476 with and $14,020 without revascularization). CONCLUSIONS: While hospitalization for ACS with revascularization procedure was associated with higher costs than hospitalization with no procedure, one-year follow-up costs were higher in the no procedure group, largely due to higher hospitalization costs.