More than 46 million people in the United States do not speak English as their primary language, and more than 21 million speak English less than "very well." Persons who have limited English proficiency are less likely to have a regular source of primary care, less likely to receive preventive care, less satisfied with care they do receive, are more likely to report problems with care and may be at increased risk of experiencing medical errors. This study assessed the impact of interpreter services on the cost and the utilization of health care services among patients with limited English proficiency. The researchers measured the change in delivery and cost of care provided to patients enrolled in a health maintenance organization before and after interpreter services were implemented. Compared with English-speaking patients, patients who used the interpreter services received significantly more recommended preventive services, made more office visits, and had more prescriptions written and filled. The estimated cost of providing interpreter services was $279 per person per year. Based on this figure the authors conclude that providing interpreter services is a financially viable method for enhancing delivery of health care to patients with limited English proficiency. Limitations of the study include small sample size, short time interval between service implementation and data collection, and limited selection of service benefit measures. The researchers also note that compared with national data, cost per interpretation in this study was excessively high (about $35 per interpretation versus $79 in this study). Interpreters were underused possibly due to overestimation of the number of interpreters needed, or lack of provider awareness about the availability of services.