Objective: Adherence to cardiovascular (CV) medications is poor. Studies that investigate interventions to improve adherence rarely consider the costs of these programs. We assessed the effectiveness and costs of different adherence-improving interventions for CV drugs. Methods: We reviewed MEDLINE to update a published literature review of interventions to improve adherence to lipid-lowering and/or antihypertensive therapy. The prior review covered January 1972-June 2002; this review covered July 2002-October 2007. Search terms included hypertension, hyperlipidemia, antihypertensive agents, antilipidemic agents, patient compliance, intervention studies and reminder system. Eligible studies evaluated at least one adherence intervention, compared an intervention to control, used an adherence measure other than self-report, and followed patients for >=6 months. Interventions were classified as dosing modifications, patient education, case management, reminders, other interventions, or combinations. Effectiveness was calculated as the ratio of adherence in the intervention group to the control group. Costs were based on those reported in the analysis, where available, or estimated based on resource use described in the article. All costs were standardized to 6 months and adjusted to 2006 dollars using the medical component of the CPI. Results: We identified 755 new articles, 5 of which met all eligibility criteria; when combined with the prior review, there were a total of 23 interventions from 14 studies. Relative improvement (RI) in adherence ranged from 1.11 to 4.65. Six month intervention costs ranged from $9.59 to $142.22 per patient. Reminders tended to have the lowest effectiveness (RI: 1.11-1.14), but were the least costly ($9.59/6 months). Case management was the most effective (RI: 1.23-4.65), but more costly than other interventions ($89.90-$129.78/6 months). Conclusion: In general, there was a positive association between the cost of the intervention and its effectiveness at improving adherence. Understanding the costs and benefits of adherence interventions may guide design and implementation of efficient adherence-improving programs.